Chore: API Improvements (#2956)

- API to fetch info of a single inbox
- Document passing custom_attributes in the API
- Ability to filter contacts with contact identifier in search API

spec/controllers/api/v1/accounts/inboxes_controller_spec.rb

@@ -44,6 +44,51 @@ RSpec.describe 'Inboxes API', type: :request do
     end
   end
 
+  describe 'GET /api/v1/accounts/{account.id}/inboxes/{inbox.id}' do
+    let(:inbox) { create(:inbox, account: account) }
+
+    context 'when it is an unauthenticated user' do
+      it 'returns unauthorized' do
+        get "/api/v1/accounts/#{account.id}/inboxes/#{inbox.id}"
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an authenticated user' do
+      let(:agent) { create(:user, account: account, role: :agent) }
+      let(:admin) { create(:user, account: account, role: :administrator) }
+      let(:inbox) { create(:inbox, account: account) }
+
+      it 'returns unauthorized for an agent who is not assigned' do
+        get "/api/v1/accounts/#{account.id}/inboxes/#{inbox.id}",
+            headers: agent.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+
+      it 'returns the inbox if administrator' do
+        get "/api/v1/accounts/#{account.id}/inboxes/#{inbox.id}",
+            headers: admin.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(JSON.parse(response.body, symbolize_names: true)[:id]).to eq(inbox.id)
+      end
+
+      it 'returns the inbox if assigned inbox is assigned as agent' do
+        create(:inbox_member, user: agent, inbox: inbox)
+        get "/api/v1/accounts/#{account.id}/inboxes/#{inbox.id}",
+            headers: agent.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(JSON.parse(response.body, symbolize_names: true)[:id]).to eq(inbox.id)
+      end
+    end
+  end
+
   describe 'GET /api/v1/accounts/{account.id}/inboxes/{inbox.id}/assignable_agents' do
     let(:inbox) { create(:inbox, account: account) }