CE changes for SSO web enforcement

Adds two methods for us to extend in EE:
- OmniauthCallbacksController#link_identity
- GroupPolicy#lookup_access_level!

app/controllers/omniauth_callbacks_controller.rb

@@ -86,7 +86,8 @@ class OmniauthCallbacksController < Devise::OmniauthCallbacksController
       log_audit_event(current_user, with: oauth['provider'])
 
       identity_linker ||= auth_module::IdentityLinker.new(current_user, oauth)
-      identity_linker.link
+
+      link_identity(identity_linker)
 
       if identity_linker.changed?
         redirect_identity_linked
@@ -100,6 +101,10 @@ class OmniauthCallbacksController < Devise::OmniauthCallbacksController
     end
   end
 
+  def link_identity(identity_linker)
+    identity_linker.link
+  end
+
   def redirect_identity_exists
     redirect_to after_sign_in_path_for(current_user)
   end

app/policies/group_policy.rb

@@ -129,6 +129,10 @@ class GroupPolicy < BasePolicy
   def access_level
     return GroupMember::NO_ACCESS if @user.nil?
 
-    @access_level ||= @subject.max_member_access_for_user(@user)
+    @access_level ||= lookup_access_level!
+  end
+
+  def lookup_access_level!
+    @subject.max_member_access_for_user(@user)
   end
 end