Add option to provide signature for a token to verify key ownership (#14054)

Add option to provide signature for a token to verify key ownership (#14054)

* Add option to provide signed token to verify key ownership

Currently we will only allow a key to be matched to a user if it matches
an activated email address. This PR provides a different mechanism - if
the user provides a signature for automatically generated token (based
on the timestamp, user creation time, user ID, username and primary
email.

* Ensure verified keys can act for all active emails for the user

* Add code to mark keys as verified

* Slight UI adjustments

* Slight UI adjustments 2

* Simplify signature verification slightly

* fix postgres test

* add api routes

* handle swapped primary-keys

* Verify the no-reply address for verified keys

* Only add email addresses that are activated to keys

* Fix committer shortcut properly

* Restructure gpg_keys.go

* Use common Verification Token code

Signed-off-by: Andrew Thornton <art27@cantab.net>