User can apply to join event

[bandungdev-com]

Feature request

Is the feature request related to a problem? Please describe

Event can only be seen, but not to join or apply to join.

Describe the solution

User can apply to join event, then the admin can approve after that.

Describe alternatives considered

It's possible if the user can join the event directly without approval, but currently most events need approval in order to hold well the attendance capacity.

Additional context

Similar with how Luma implement the registration flow with apply to join

This will need to create a new model like EventAttendee and there will be approval status