Bug : Fix race conditions in the signup endpoint.

[epicadk]

Describe the bug

If two users send requests to the register endpoint at the same time and both have the same username/emailID then the backend will crash.

To Reproduce
Kind of hard to do this however it can be done programmatically as explained here

Expected behavior

The app should not crash and instead return an error saying that the username is already taken to one of the users and register the other successfully.

Same as anitab-org/mentorship-backend#1019

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[epicadk]

If this is valid I would like to work on this : ).

[NenadPantelic]

This is not the only race condition case we have 🙂. #83 will support this, but we need to recode controller logic.

[epicadk]

This is not the only race condition case we have 🙂. #83 will support this, but we need to recode controller logic.

Yes I did read that however I thought that would be limited to adding constraints in the database and this would fix the race conditions. Because even in mentorship we do have constraints and still have race conditions present. That's why I think this is a valid issue. What do you think?

[NenadPantelic]

We definitely need database constraints, based on them, we will get integrity errors we should catch and return meaningful messages with status code.