User CRUD endpoints on backend

[mozsarmate]

Endpoints:

GET /users

• This should return all the users and it should be pageable. (Normal users read only one, most of the time)
• The list returned needs to be sorted by name (maybe there should be a sort_by parameter?)
• We need to allow filtering
• For pagination it should accept a page parameter for the current page index (starting from 0) and a page_size parameter for the number of items on each page
• The backend needs to check if the current user has permission to do it

GET /users/me

• Returns the current user
• It somewhat collides with the next endpoint, but all the usersId-s are numbers, so it shouldn't be a problem

GET /users/{userId}

• The backend needs to check if the current user has permission to do it

PATCH /users/{userId}

• Modifies a user profile
• The backend needs to check if the current user has permission to do it