Update `Groups::EnterpriseUsers::CreateService` according to the Enterprise User definition change

As a part of #385785 (closed) we added Groups::EnterpriseUsers::CreateService service class that receives group and user. It marks the user Enterprise User of the group if they meet the condition.

• As per #396384 (closed), we changed the Enterprise User definition in the following MR gitlab-com/www-gitlab-com!121353 (merged). The implementation of the service class should reflect the updated Enterprise User definition, see https://about.gitlab.com/handbook/support/workflows/gitlab-com_overview.html#enterprise-users

• As per #396384 (comment 1313453335) we should add new attributes enterprise_group_id and enterprise_group_associated_at to user_details table and mark a user as an enterprise user by using those attributes instead of provisioned_by_group_id and provisioned_by_group_at.

• The service class should allow enterprise users of group1 to become enterprise users of group2 in case of moving verified domains from group1 to group2.