Fully revoke signout tokens and update last_revoke_checked

[sethvargo]

⚠️ We should talk about whether to actually revoke refresh tokens! Revoking the refresh token ensures a signout, and it occurs on all devices. That means for local testing, if one person logs out, we all get logged out (we'll need to make our own accounts for testing auth). I think this is probably the best solution, but open to other ideas.

Release Note

Fully revoke signout tokens and update last_revoke_checked

/assign @mikehelmick
/assign @whaught

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