This commit adds gpg system integration. This is done through two new
packages: gpgbin, which handles the system calls and parsing; and gpg
which is mostly a copy of emersion/go-pgpmail with modifications to
interface with package gpgbin. gpg includes tests for many cases, and
by it's nature also tests package gpgbin. I separated these in case an
external dependency is ever used for the gpg sys-calls/parsing (IE we
mirror how go-pgpmail+openpgp currently are dependencies)
Two new config options are introduced:
* pgp-provider. If it is not explicitly set to "gpg", aerc will default to
it's internal pgp provider
* pgp-key-id: (Optionally) specify a key by short or long keyId
Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>
