Backport to v1.2 of PR 2266 2467 2663 (#2788)

* Only check at least one email gpg key (#2266)

* Only require one email (possibly not yet validated)

* Update message error and check validation of commit

* Add integrations tests

* Complete integration for import

* Add pre-check/optimization

* Add some test (not finished)

* Finish

* Fix fixtures

* Fix typo

* Don't guess key ID

* Make repo private to no interfere with other tests (#2467)

* GPG key email verification no longer case sensitive (#2661) (#2663)

* GPG key email verification no longer case sensitive (#2661)

* case insensitive GPG key email verification now cached (#2661)

Signed-off-by: Julian Scholle <julian.scholle@googlemail.com>

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