Added API routes to create and delete users

[oliverbates94]

Hi! I'm not sure if this is the right approach to this, I basically duplicated the code from the UserController, but I needed these two API routes

Tell me if there's something I need to change!

[tchapi]

Thanks for the work. I'm overall ok for these two new APIs, but we need to make them right 🙏🏼

Apart from the in-line comments above:

• Most lines are copy-pasted from Admin\UserController::userCreate/userDelete. Utils::createPasswordlessUserWithDefaultObjects() already exists and does 90% of the create path; I think the right move is to extend Utils (e.g. createUserWithDefaultObjects(username, displayName, email, password, isAdmin) and a deleteUserAndObjects(User) or something like that) and call it from both controllers.

• No email validation. The admin path gets EmailType + Assert\Email on Principal::$email via the form validator but the API path never runs the validator, so any string is stored as an email (which then ends up in mailto: share hrefs).

• I'll need some functional test added under tests/Functional + update of docs/api

[oliverbates94]

Hi, I addressed all your comments

I have some doubts about the "userCreate" implementation in the UserController: maybe it would be cleaner to split the create and edit functionality in two functions, let me know