Restructure omni services and add Chatwoot research snapshot

research/chatwoot/app/controllers/linear/callbacks_controller.rb

@@ -0,0 +1,73 @@
+class Linear::CallbacksController < ApplicationController
+  include Linear::IntegrationHelper
+
+  def show
+    @response = oauth_client.auth_code.get_token(
+      params[:code],
+      redirect_uri: "#{base_url}/linear/callback"
+    )
+
+    handle_response
+  rescue StandardError => e
+    Rails.logger.error("Linear callback error: #{e.message}")
+    redirect_to linear_redirect_uri
+  end
+
+  private
+
+  def oauth_client
+    app_id = GlobalConfigService.load('LINEAR_CLIENT_ID', nil)
+    app_secret = GlobalConfigService.load('LINEAR_CLIENT_SECRET', nil)
+
+    OAuth2::Client.new(
+      app_id,
+      app_secret,
+      {
+        site: 'https://api.linear.app',
+        token_url: '/oauth/token',
+        authorize_url: '/oauth/authorize'
+      }
+    )
+  end
+
+  def handle_response
+    hook = account.hooks.new(
+      access_token: parsed_body['access_token'],
+      status: 'enabled',
+      app_id: 'linear',
+      settings: {
+        token_type: parsed_body['token_type'],
+        expires_in: parsed_body['expires_in'],
+        scope: parsed_body['scope']
+      }
+    )
+    # You may wonder why we're not handling the refresh token update, since the token will expire only after 10 years, https://github.com/linear/linear/issues/251
+    hook.save!
+    redirect_to linear_redirect_uri
+  rescue StandardError => e
+    Rails.logger.error("Linear callback error: #{e.message}")
+    redirect_to linear_redirect_uri
+  end
+
+  def account
+    @account ||= Account.find(account_id)
+  end
+
+  def account_id
+    return unless params[:state]
+
+    verify_linear_token(params[:state])
+  end
+
+  def linear_redirect_uri
+    "#{ENV.fetch('FRONTEND_URL', nil)}/app/accounts/#{account.id}/settings/integrations/linear"
+  end
+
+  def parsed_body
+    @parsed_body ||= @response.response.parsed
+  end
+
+  def base_url
+    ENV.fetch('FRONTEND_URL', 'http://localhost:3000')
+  end
+end