Default Roles For User Registration/Creation

Feature: Be able to set a role as the default role so that a user gets created with this role already assigned.

Description: Post user registration, either via universal login or management API, a user is created with the default role, instead of no roles as is currently the case. A role would be selected as the default role. All users created via universal login or the management API will receive the default roles.

Use-case: The API has strict role-based access requirements, a user with no role can not make requests. A workaround to the current implementation is to create a post-login action to check whether the user has any roles, if the user has no roles, assign the default role using the management API. Having this post-login action feels unnecessary.