Implement (or clarify) the ability to pre-link/pre-authorize Google accounts by email address

[nekohayo]

My usecase is that I want to be able, ideally, to create user accounts for people (professors, researchers, etc.) I work with inside a research lab, and to do so with as little friction as possible, by creating the accounts and telling kanboard "this is their google/gapps email address, allow that person to be authentified with that".

What I found out today after a long time of not understanding why they couldn't login with their google account even if the addresses matched and were set as the google "id" for the external login mechanism, is that this doesn't seem to be tied to the email address at all, in practice. When I do that, if they try to log in with their google account, they always get thrown back to Kanboard's login page (after logging into their google account) with the non-descript error message that says "External authentication failed".

It turns out that for this to work, it seems, I really need to create a user account "with password" for them, have them personally log into kanboard with that local account, then they need to go to their user profile and into the "External accounts" section, and click "Link my Google account". And then it works for them. But I can't be the one to "pre-link/pre-authorize" their google account.

So either I'm encountering a bug, or this is really the design you intended but the user interface doesn't make that totally clear (and the documentation in https://github.com/kanboard/plugin-google-auth/blob/master/README.md somewhat hints at this, but it is not 110% clear). If the latter, then I think we could improve the UI a bit (or at least have some sort of help label next to the "Google ID" field in the "Edit Authentication" section of a user profile, to say "Note: the Google ID is a unique number ID, NOT the email address! The user needs to link the account themselves by first logging into the account in kanboard." And you could add that kind of information in the readme in addition to the UI.

But if it's a bug, then that's a different matter altogether :)