feat(signup): allow to block signup

[arthurdotwork]

fixes #3201.

I assumed that the flow would look like this; you start with the signup being enabled (which is the default value if the environment variable is not set), you first register to create the owner account/workspace and then, when you are done, you can now disable the registration of new users. There is still an exception; users who have a workspaceInviteHash are free to enter.

[github-actions]

	Warnings
⚠️	Changes were made to the environment variables, but not to the documentation - Please review your changes and check if a change needs to be documented!

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[FelixMalfait]

Oh yes good catch on the inviteHash, forgot to mention that!

[arthurdotwork]

Tests were failing since I had forgotten to update the service declaration. That should be OK now.

[charlesBochet]

Thank you, this is a great initiative.
I believe we also have some work on the frontend. Could you pass this environment variable value through ClientConfig. You will be able to get it in the frontend, store it in a recoilstate and use it in PageChangeEffect to prevent any user to access /sign-up route with no workspaceHash (you should redirect to /sign-in in this case)

[arthurdotwork]

Hey there! 👋

Finally went through all of this GraphQL thing and was able to complete the frontend part.

CleanShot.2024-01-05.at.21.36.27.mp4

[charlesBochet]

Looks great! I'm taking a final look and will merge it this morning :)

[charlesBochet]

@arthureichelberger I have tested all cases and I have actually removed the override of checkUserExists in case of disabled sign up. This is preventing users to be added through inviteLink.

I feel the frontend approach is better now that we have it.
So it will still be possible to list users but I feel it's OK