feat: add saml model & controller [CW-2958] (#12289)

This PR adds the foundation for account-level SAML SSO configuration in
Chatwoot Enterprise. It introduces a new `AccountSamlSettings` model and
management API that allows accounts to configure their own SAML identity
providers independently, this also includes the certificate generation
flow

The implementation includes a new controller
(`Api::V1::Accounts::SamlSettingsController`) that provides CRUD
operations for SAML configuration

The feature is properly gated behind the 'saml' feature flag and
includes administrator-only authorization via Pundit policies.

spec/enterprise/controllers/api/v1/accounts/saml_settings_controller_spec.rb

@@ -0,0 +1,265 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Api::V1::Accounts::SamlSettings', type: :request do
+  let(:account) { create(:account) }
+  let(:agent) { create(:user, account: account, role: :agent) }
+  let(:administrator) { create(:user, account: account, role: :administrator) }
+
+  before do
+    account.enable_features('saml')
+    account.save!
+  end
+
+  def json_response
+    JSON.parse(response.body, symbolize_names: true)
+  end
+
+  describe 'GET /api/v1/accounts/{account.id}/saml_settings' do
+    context 'when unauthenticated' do
+      it 'returns unauthorized' do
+        get "/api/v1/accounts/#{account.id}/saml_settings"
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when authenticated as administrator' do
+      context 'when SAML settings exist' do
+        let(:saml_settings) do
+          create(:account_saml_settings,
+                 account: account,
+                 sso_url: 'https://idp.example.com/saml/sso',
+                 role_mappings: { 'Admins' => { 'role' => 1 } })
+        end
+
+        before do
+          saml_settings # Ensure the record exists
+        end
+
+        it 'returns the SAML settings' do
+          get "/api/v1/accounts/#{account.id}/saml_settings",
+              headers: administrator.create_new_auth_token,
+              as: :json
+
+          expect(response).to have_http_status(:success)
+          expect(json_response[:sso_url]).to eq('https://idp.example.com/saml/sso')
+          expect(json_response[:role_mappings]).to eq({ Admins: { role: 1 } })
+        end
+      end
+
+      context 'when SAML settings do not exist' do
+        it 'returns default SAML settings' do
+          get "/api/v1/accounts/#{account.id}/saml_settings",
+              headers: administrator.create_new_auth_token,
+              as: :json
+
+          expect(response).to have_http_status(:success)
+          expect(json_response[:role_mappings]).to eq({})
+        end
+      end
+    end
+
+    context 'when authenticated as agent' do
+      it 'returns unauthorized' do
+        get "/api/v1/accounts/#{account.id}/saml_settings",
+            headers: agent.create_new_auth_token
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when SAML feature is not enabled' do
+      before do
+        account.disable_features('saml')
+        account.save!
+      end
+
+      it 'returns forbidden with feature not enabled message' do
+        get "/api/v1/accounts/#{account.id}/saml_settings",
+            headers: administrator.create_new_auth_token
+
+        expect(response).to have_http_status(:forbidden)
+      end
+    end
+  end
+
+  describe 'POST /api/v1/accounts/{account.id}/saml_settings' do
+    let(:valid_params) do
+      key = OpenSSL::PKey::RSA.new(2048)
+      cert = OpenSSL::X509::Certificate.new
+      cert.version = 2
+      cert.serial = 1
+      cert.subject = OpenSSL::X509::Name.parse('/C=US/ST=Test/L=Test/O=Test/CN=test.example.com')
+      cert.issuer = cert.subject
+      cert.public_key = key.public_key
+      cert.not_before = Time.zone.now
+      cert.not_after = cert.not_before + (365 * 24 * 60 * 60)
+      cert.sign(key, OpenSSL::Digest.new('SHA256'))
+
+      {
+        saml_settings: {
+          sso_url: 'https://idp.example.com/saml/sso',
+          certificate: cert.to_pem,
+          idp_entity_id: 'https://idp.example.com/saml/metadata',
+          role_mappings: { 'Admins' => { 'role' => 1 }, 'Users' => { 'role' => 0 } }
+        }
+      }
+    end
+
+    context 'when unauthenticated' do
+      it 'returns unauthorized' do
+        post "/api/v1/accounts/#{account.id}/saml_settings", params: valid_params
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when authenticated as administrator' do
+      context 'with valid parameters' do
+        it 'creates SAML settings' do
+          expect do
+            post "/api/v1/accounts/#{account.id}/saml_settings",
+                 params: valid_params,
+                 headers: administrator.create_new_auth_token,
+                 as: :json
+          end.to change(AccountSamlSettings, :count).by(1)
+
+          expect(response).to have_http_status(:success)
+
+          saml_settings = AccountSamlSettings.find_by(account: account)
+          expect(saml_settings.sso_url).to eq('https://idp.example.com/saml/sso')
+          expect(saml_settings.role_mappings).to eq({ 'Admins' => { 'role' => 1 }, 'Users' => { 'role' => 0 } })
+        end
+      end
+
+      context 'with invalid parameters' do
+        let(:invalid_params) do
+          valid_params.tap do |params|
+            params[:saml_settings][:sso_url] = nil
+          end
+        end
+
+        it 'returns unprocessable entity' do
+          post "/api/v1/accounts/#{account.id}/saml_settings",
+               params: invalid_params,
+               headers: administrator.create_new_auth_token,
+               as: :json
+
+          expect(response).to have_http_status(:unprocessable_entity)
+          expect(AccountSamlSettings.count).to eq(0)
+        end
+      end
+    end
+
+    context 'when authenticated as agent' do
+      it 'returns unauthorized' do
+        post "/api/v1/accounts/#{account.id}/saml_settings",
+             params: valid_params,
+             headers: agent.create_new_auth_token
+
+        expect(response).to have_http_status(:unauthorized)
+        expect(AccountSamlSettings.count).to eq(0)
+      end
+    end
+  end
+
+  describe 'PUT /api/v1/accounts/{account.id}/saml_settings' do
+    let(:saml_settings) do
+      create(:account_saml_settings,
+             account: account,
+             sso_url: 'https://old.example.com/saml')
+    end
+    let(:update_params) do
+      key = OpenSSL::PKey::RSA.new(2048)
+      cert = OpenSSL::X509::Certificate.new
+      cert.version = 2
+      cert.serial = 3
+      cert.subject = OpenSSL::X509::Name.parse('/C=US/ST=Test/L=Test/O=Test/CN=update.example.com')
+      cert.issuer = cert.subject
+      cert.public_key = key.public_key
+      cert.not_before = Time.zone.now
+      cert.not_after = cert.not_before + (365 * 24 * 60 * 60)
+      cert.sign(key, OpenSSL::Digest.new('SHA256'))
+
+      {
+        saml_settings: {
+          sso_url: 'https://new.example.com/saml/sso',
+          certificate: cert.to_pem,
+          role_mappings: { 'NewGroup' => { 'custom_role_id' => 5 } }
+        }
+      }
+    end
+
+    before do
+      saml_settings # Ensure the record exists
+    end
+
+    context 'when unauthenticated' do
+      it 'returns unauthorized' do
+        put "/api/v1/accounts/#{account.id}/saml_settings", params: update_params
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when authenticated as administrator' do
+      it 'updates SAML settings' do
+        put "/api/v1/accounts/#{account.id}/saml_settings",
+            params: update_params,
+            headers: administrator.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+
+        saml_settings.reload
+        expect(saml_settings.sso_url).to eq('https://new.example.com/saml/sso')
+        expect(saml_settings.role_mappings).to eq({ 'NewGroup' => { 'custom_role_id' => 5 } })
+      end
+    end
+
+    context 'when authenticated as agent' do
+      it 'returns unauthorized' do
+        put "/api/v1/accounts/#{account.id}/saml_settings",
+            params: update_params,
+            headers: agent.create_new_auth_token
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+  end
+
+  describe 'DELETE /api/v1/accounts/{account.id}/saml_settings' do
+    let(:saml_settings) { create(:account_saml_settings, account: account) }
+
+    before do
+      saml_settings # Ensure the record exists
+    end
+
+    context 'when unauthenticated' do
+      it 'returns unauthorized' do
+        delete "/api/v1/accounts/#{account.id}/saml_settings"
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when authenticated as administrator' do
+      it 'destroys SAML settings' do
+        expect do
+          delete "/api/v1/accounts/#{account.id}/saml_settings",
+                 headers: administrator.create_new_auth_token
+        end.to change(AccountSamlSettings, :count).by(-1)
+
+        expect(response).to have_http_status(:no_content)
+      end
+    end
+
+    context 'when authenticated as agent' do
+      it 'returns unauthorized' do
+        delete "/api/v1/accounts/#{account.id}/saml_settings",
+               headers: agent.create_new_auth_token
+
+        expect(response).to have_http_status(:unauthorized)
+        expect(AccountSamlSettings.count).to eq(1)
+      end
+    end
+  end
+end