Major changes: logic add to panel, local variables, panel histor, users management...

internal/datasource/synthetic/synthetic.go

@@ -85,6 +85,22 @@ func (s *Synthetic) ListSignals(_ context.Context) ([]datasource.Metadata, error
 	return out, nil
 }
 
+// FilteredMetadata returns metadata for every defined synthetic signal for
+// which keep returns true. It lets the API layer apply per-caller visibility
+// rules (which depend on SignalDef fields not present in datasource.Metadata).
+func (s *Synthetic) FilteredMetadata(keep func(SignalDef) bool) []datasource.Metadata {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	out := make([]datasource.Metadata, 0, len(s.signals))
+	for _, st := range s.signals {
+		if keep(st.def) {
+			out = append(out, defToMetadata(st.def))
+		}
+	}
+	return out
+}
+
 // GetMetadata returns metadata for a single named signal.
 func (s *Synthetic) GetMetadata(_ context.Context, signal string) (datasource.Metadata, error) {
 	s.mu.RLock()