feat: Control the allowed login methods via Super Admin (#12892)

- Control the allowed authentication methods for a chatwoot installation
via super admin configs. [SAML, Google Auth etc]
------
[Codex
Task](https://chatgpt.com/codex/tasks/task_e_6917d503b6e48326a261672c1de91462)

---------

Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

enterprise/app/controllers/enterprise/super_admin/app_configs_controller.rb

@@ -11,6 +11,8 @@ module Enterprise::SuperAdmin::AppConfigsController
       @allowed_configs = internal_config_options
     when 'captain'
       @allowed_configs = captain_config_options
+    when 'saml'
+      @allowed_configs = saml_config_options
     else
       super
     end
@@ -46,4 +48,8 @@ module Enterprise::SuperAdmin::AppConfigsController
       CAPTAIN_FIRECRAWL_API_KEY
     ]
   end
+
+  def saml_config_options
+    %w[ENABLE_SAML_SSO_LOGIN]
+  end
 end