feat: Added the ability to create Instagram channel (#11182)

This PR is part of https://github.com/chatwoot/chatwoot/pull/11054 to
make the review cycle easier.

app/controllers/instagram/callbacks_controller.rb

@@ -0,0 +1,123 @@
+class Instagram::CallbacksController < ApplicationController
+  include InstagramConcern
+  include Instagram::IntegrationHelper
+
+  def show
+    # Check if Instagram redirected with an error (user canceled authorization)
+    # See: https://developers.facebook.com/docs/instagram-platform/instagram-api-with-instagram-login/business-login#canceled-authorization
+    if params[:error].present?
+      handle_authorization_error
+      return
+    end
+
+    process_successful_authorization
+  rescue StandardError => e
+    handle_error(e)
+  end
+
+  private
+
+  # Process the authorization code and create inbox
+  def process_successful_authorization
+    @response = instagram_client.auth_code.get_token(
+      oauth_code,
+      redirect_uri: "#{base_url}/#{provider_name}/callback",
+      grant_type: 'authorization_code'
+    )
+
+    @long_lived_token_response = exchange_for_long_lived_token(@response.token)
+    inbox, = create_channel_with_inbox
+    redirect_to app_instagram_inbox_agents_url(account_id: account_id, inbox_id: inbox.id)
+  end
+
+  # Handle all errors that might occur during authorization
+  # https://developers.facebook.com/docs/instagram-platform/instagram-api-with-instagram-login/business-login#sample-rejected-response
+  def handle_error(error)
+    Rails.logger.error("Instagram Channel creation Error: #{error.message}")
+    ChatwootExceptionTracker.new(error).capture_exception
+
+    error_info = extract_error_info(error)
+    redirect_to_error_page(error_info)
+  end
+
+  # Extract error details from the exception
+  def extract_error_info(error)
+    if error.is_a?(OAuth2::Error)
+      begin
+        # Instagram returns JSON error response which we parse to extract error details
+        JSON.parse(error.message)
+      rescue JSON::ParseError
+        # Fall back to a generic OAuth error if JSON parsing fails
+        { 'error_type' => 'OAuthException', 'code' => 400, 'error_message' => error.message }
+      end
+    else
+      # For other unexpected errors
+      { 'error_type' => error.class.name, 'code' => 500, 'error_message' => error.message }
+    end
+  end
+
+  # Handles the case when a user denies permissions or cancels the authorization flow
+  # Error parameters are documented at:
+  # https://developers.facebook.com/docs/instagram-platform/instagram-api-with-instagram-login/business-login#canceled-authorization
+  def handle_authorization_error
+    error_info = {
+      'error_type' => params[:error] || 'authorization_error',
+      'code' => 400,
+      'error_message' => params[:error_description] || 'Authorization was denied'
+    }
+
+    Rails.logger.error("Instagram Authorization Error: #{error_info['error_message']}")
+    redirect_to_error_page(error_info)
+  end
+
+  # Centralized method to redirect to error page with appropriate parameters
+  # This ensures consistent error handling across different error scenarios
+  # Frontend will handle the error page based on the error_type
+  def redirect_to_error_page(error_info)
+    redirect_to app_new_instagram_inbox_url(
+      account_id: account_id,
+      error_type: error_info['error_type'],
+      code: error_info['code'],
+      error_message: error_info['error_message']
+    )
+  end
+
+  def create_channel_with_inbox
+    ActiveRecord::Base.transaction do
+      expires_at = Time.current + @long_lived_token_response['expires_in'].seconds
+
+      user_details = fetch_instagram_user_details(@long_lived_token_response['access_token'])
+
+      channel_instagram = Channel::Instagram.create!(
+        access_token: @long_lived_token_response['access_token'],
+        instagram_id: user_details['user_id'].to_s,
+        account: account,
+        expires_at: expires_at
+      )
+
+      account.inboxes.create!(
+        account: account,
+        channel: channel_instagram,
+        name: user_details['username']
+      )
+    end
+  end
+
+  def account_id
+    return unless params[:state]
+
+    verify_instagram_token(params[:state])
+  end
+
+  def oauth_code
+    params[:code]
+  end
+
+  def account
+    @account ||= Account.find(account_id)
+  end
+
+  def provider_name
+    'instagram'
+  end
+end