Resolve "Deprovision and update users from a configured identity provider"

What does this MR do?

This adds the SCIM protocol - as an API to GitLab

It implements the deprovision endpoint, plus a few more that are needed in order for the sync to work.

It still reuses the grape's API, but it is updated so it's compatible with the protocol (the version of the endpoints need to match SCIM version, the JSON is not generic but matches SCIM's protocol, etc...)

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

Closes #5014 (closed)


Edited by James Lopez