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>

app/controllers/dashboard_controller.rb

@@ -78,10 +78,18 @@ class DashboardController < ActionController::Base
       WHATSAPP_CONFIGURATION_ID: GlobalConfigService.load('WHATSAPP_CONFIGURATION_ID', ''),
       IS_ENTERPRISE: ChatwootApp.enterprise?,
       AZURE_APP_ID: GlobalConfigService.load('AZURE_APP_ID', ''),
-      GIT_SHA: GIT_HASH
+      GIT_SHA: GIT_HASH,
+      ALLOWED_LOGIN_METHODS: allowed_login_methods
     }
   end
 
+  def allowed_login_methods
+    methods = ['email']
+    methods << 'google_oauth' if GlobalConfigService.load('ENABLE_GOOGLE_OAUTH_LOGIN', 'true').to_s != 'false'
+    methods << 'saml' if ChatwootHub.pricing_plan != 'community' && GlobalConfigService.load('ENABLE_SAML_SSO_LOGIN', 'true').to_s != 'false'
+    methods
+  end
+
   def set_application_pack
     @application_pack = if request.path.include?('/auth') || request.path.include?('/login')
                           'v3app'