Add rudimentary database watcher

Adds a simple database watcher. At this point it's just one process, but
the plan is to allow different implementations that inform the local running
workers of changes that have occured on entities of interest in the database.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

database/sql/util.go

@@ -26,6 +26,7 @@ import (
 	runnerErrors "github.com/cloudbase/garm-provider-common/errors"
 	commonParams "github.com/cloudbase/garm-provider-common/params"
 	"github.com/cloudbase/garm-provider-common/util"
+	dbCommon "github.com/cloudbase/garm/database/common"
 	"github.com/cloudbase/garm/params"
 )
 
@@ -467,3 +468,31 @@ func (s *sqlDatabase) hasGithubEntity(tx *gorm.DB, entityType params.GithubEntit
 	}
 	return nil
 }
+
+func (s *sqlDatabase) marshalAndSeal(data interface{}) ([]byte, error) {
+	enc, err := json.Marshal(data)
+	if err != nil {
+		return nil, errors.Wrap(err, "marshalling data")
+	}
+	return util.Seal(enc, []byte(s.cfg.Passphrase))
+}
+
+func (s *sqlDatabase) unsealAndUnmarshal(data []byte, target interface{}) error {
+	decrypted, err := util.Unseal(data, []byte(s.cfg.Passphrase))
+	if err != nil {
+		return errors.Wrap(err, "decrypting data")
+	}
+	if err := json.Unmarshal(decrypted, target); err != nil {
+		return errors.Wrap(err, "unmarshalling data")
+	}
+	return nil
+}
+
+func (s *sqlDatabase) sendNotify(entityType dbCommon.DatabaseEntityType, op dbCommon.OperationType, payload interface{}) {
+	message := dbCommon.ChangePayload{
+		Operation:  op,
+		Payload:    payload,
+		EntityType: entityType,
+	}
+	s.producer.Notify(message)
+}