continue work on notifs, tidy some stuff up elsewhere

internal/federation/federatingdb/exists.go

@@ -0,0 +1,24 @@
+package federatingdb
+
+import (
+	"context"
+	"net/url"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Exists returns true if the database has an entry for the specified
+// id. It may not be owned by this application instance.
+//
+// The library makes this call only after acquiring a lock first.
+func (f *federatingDB) Exists(c context.Context, id *url.URL) (exists bool, err error) {
+	l := f.log.WithFields(
+		logrus.Fields{
+			"func": "Exists",
+			"id":   id.String(),
+		},
+	)
+	l.Debugf("entering EXISTS function with id %s", id.String())
+
+	return false, nil
+}