Pad GPG Key ID with preceding zeroes (#20878) (#20885)

Backport #20878

The go crypto library does not pad keyIDs to 16 characters with preceding zeroes. This
is a somewhat confusing thing for most users who expect these to have preceding zeroes.

This PR prefixes any sub 16 length KeyID with preceding zeroes and removes preceding
zeroes from KeyIDs inputted on the API.

Fix #20876

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

models/asymkey/gpg_key.go

@@ -63,6 +63,15 @@ func (key *GPGKey) AfterLoad(session *xorm.Session) {
 	}
 }
 
+// PaddedKeyID show KeyID padded to 16 characters
+func (key *GPGKey) PaddedKeyID() string {
+	if len(key.KeyID) > 15 {
+		return key.KeyID
+	}
+	zeros := "0000000000000000"
+	return zeros[0:16-len(key.KeyID)] + key.KeyID
+}
+
 // ListGPGKeys returns a list of public keys belongs to given user.
 func ListGPGKeys(ctx context.Context, uid int64, listOptions db.ListOptions) ([]*GPGKey, error) {
 	sess := db.GetEngine(ctx).Table(&GPGKey{}).Where("owner_id=? AND primary_key_id=''", uid)