feat(auth): ability to delete provider in auth

[hardikns]

This address #578,
Adds the feature in the python admin sdk (which has been present in the nodejs sdk) that will allow users to delete providers (like google.com, facebook.com). Basically add delete_providers as input to update_user method in auth.

[hiranya911]

Thank for the PR @hardikns. There's an open PR #383 that implements this feature, but I'm not sure if the original authors are still available to finish up the work.

@rsgowman @bojeil-google @nrsim are any of you available to finish and merge #383? If not we can accept this PR by @hardikns (it will likely need some minor changes to meet the approved API design).

[bojeil-google]

If @rsgowman or @nrsim are unable to finish the pending PR, perhaps, we can accept @hardikns PR (adjusted to meet the approved API design) especially if it only needs minor changes?

[rsgowman]

Ah, sorry; I forgot this was still outstanding. I don't think @nrsim will be available to finish #383, at least not for some time.

@hardikns's PR has the advantage of not having to resolve 1y+ worth of merge conflicts. Though #383 also does linking (whereas this one just deletes).

Since this PR likely only needs minor revision, we can probably get this one submitted quicker than #383. (And I assume @hardikns is waiting on this feature.) My vote is to proceed with this, and then rebase 383 ontop of this one.

My only hesitation is that the provider_to_link parameter should ideally appear before the providers_to_delete parameter in the update_user function. Or at least, I think that's the ordering on the other platforms.

[hiranya911]

Thanks everybody for the comments. I've reviewed the PR with the expectation that we will accept and merge this before #383.

@hardikns PR looks pretty good. I've pointed out a few things that can be improved.

[hiranya911]

Thanks @hardikns. LGTM with a few nits. I can merge once those comments are addressed.

[hardikns]

@hiranya911 I have addressed your comments and also updated my branch. Let me know if anything else is pending.