Introduce Gitlab::Auth.omniauth_setup_providers

Which could extend from EE

config/initializers/omniauth.rb

@@ -19,11 +19,5 @@ end
 
 if Gitlab.config.omniauth.enabled
   provider_names = Gitlab.config.omniauth.providers.map(&:name)
-  require 'omniauth-kerberos' if provider_names.include?('kerberos')
-
-  Gitlab::Auth.omniauth_providers.each do |provider|
-    if provider_names.include?(provider)
-      require_dependency "omni_auth/strategies/#{provider}"
-    end
-  end
+  Gitlab::Auth.omniauth_setup_providers(provider_names)
 end

lib/gitlab/auth.rb

@@ -14,8 +14,23 @@ module Gitlab
     DEFAULT_SCOPES = [:api].freeze
 
     class << self
-      def omniauth_providers
-        %w[bitbucket jwt]
+      def omniauth_customized_providers
+        @omniauth_customized_providers ||= %w[bitbucket jwt]
+      end
+
+      def omniauth_setup_providers(provider_names)
+        provider_names.each do |provider|
+          omniauth_setup_a_provider(provider)
+        end
+      end
+
+      def omniauth_setup_a_provider(provider)
+        case provider
+        when 'kerberos'
+          require 'omniauth-kerberos'
+        when *omniauth_customized_providers
+          require_dependency "omni_auth/strategies/#{provider}"
+        end
       end
 
       def find_for_git_client(login, password, project:, ip:)