chore: add oauth flow

app/helpers/github/integration_helper.rb

@@ -0,0 +1,47 @@
+module Github::IntegrationHelper
+  # Generates a signed JWT token for Github integration
+  #
+  # @param account_id [Integer] The account ID to encode in the token
+  # @return [String, nil] The encoded JWT token or nil if client secret is missing
+  def generate_github_token(account_id)
+    return if client_secret.blank?
+
+    JWT.encode(token_payload(account_id), client_secret, 'HS256')
+  rescue StandardError => e
+    Rails.logger.error("Failed to generate Github token: #{e.message}")
+    nil
+  end
+
+  def token_payload(account_id)
+    {
+      sub: account_id,
+      iat: Time.current.to_i
+    }
+  end
+
+  # Verifies and decodes a Github JWT token
+  #
+  # @param token [String] The JWT token to verify
+  # @return [Integer, nil] The account ID from the token or nil if invalid
+  def verify_github_token(token)
+    return if token.blank? || client_secret.blank?
+
+    decode_token(token, client_secret)
+  end
+
+  private
+
+  def client_secret
+    @client_secret ||= GlobalConfigService.load('GITHUB_CLIENT_SECRET', nil)
+  end
+
+  def decode_token(token, secret)
+    JWT.decode(token, secret, true, {
+                 algorithm: 'HS256',
+                 verify_expiration: true
+               }).first['sub']
+  rescue StandardError => e
+    Rails.logger.error("Unexpected error verifying Github token: #{e.message}")
+    nil
+  end
+end