[$75] Existing user handling

[jmgasper]

@veshu - When using the links in "Git access control", we need to handle projects that are already set up in Gitlab / Github, but are being added to Topcoder-X.

What this means is that the users may already have access in Gitlab / Github, but aren't mapped properly in Topcoder-X.

Right now, this is causing problems because the flow errors out at {“message”:“Failed to add group member. Conflict. Detail: Member already exists”,“code”:“Member already exists”}, without first adding the user mapping into Topcoder-X.

We need to make sure that even if the user is already active on a project that we still make sure the mapping is updated / added appropriately.