Add API endpoints for resource metadata management (ownership & permissions)

New types: UpdateResourceMetadataRequest and GetResourceMetadataResponse in types.go
    AuthService methods: StoreResourceMetadata and GetResourceMetadata in auth/auth.go
    Handlers: getResourceMetadataHandler and updateResourceMetadataHandler in server/handlers.go
    Routes: /kv/{path}/metadata (GET for read, PUT for update) with auth middleware in server/routes.go

Enables fine-grained control over KV path ownership, group assignments, and POSIX-inspired permissions.

server/handlers.go

@@ -1271,3 +1271,142 @@ func (s *Server) getRevisionHistory(key string) ([]map[string]interface{}, error
 func (s *Server) getSpecificRevision(key string, revision int) (*types.StoredValue, error) {
 	return s.revisionService.GetSpecificRevision(key, revision)
 }
+
+// getResourceMetadataHandler retrieves metadata for a resource path
+func (s *Server) getResourceMetadataHandler(w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	path := vars["path"]
+
+	authCtx := auth.GetAuthContext(r.Context())
+	if authCtx == nil {
+		http.Error(w, "Unauthorized", http.StatusUnauthorized)
+		return
+	}
+
+	// Check read permission on the resource
+	if !s.authService.CheckResourcePermission(authCtx, path, "read") {
+		http.Error(w, "Forbidden", http.StatusForbidden)
+		return
+	}
+
+	metadata, err := s.authService.GetResourceMetadata(path)
+	if err == badger.ErrKeyNotFound {
+		// Return default metadata if not found
+		defaultMetadata := types.ResourceMetadata{
+			OwnerUUID:   authCtx.UserUUID,
+			GroupUUID:   "",
+			Permissions: types.DefaultPermissions,
+			CreatedAt:   time.Now().Unix(),
+			UpdatedAt:   time.Now().Unix(),
+		}
+		metadata = &defaultMetadata
+	} else if err != nil {
+		s.logger.WithError(err).WithField("path", path).Error("Failed to get resource metadata")
+		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		return
+	}
+
+	response := types.GetResourceMetadataResponse{
+		OwnerUUID:   metadata.OwnerUUID,
+		GroupUUID:   metadata.GroupUUID,
+		Permissions: metadata.Permissions,
+		TTL:         metadata.TTL,
+		CreatedAt:   metadata.CreatedAt,
+		UpdatedAt:   metadata.UpdatedAt,
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(response)
+}
+
+// updateResourceMetadataHandler updates metadata for a resource path
+func (s *Server) updateResourceMetadataHandler(w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	path := vars["path"]
+
+	authCtx := auth.GetAuthContext(r.Context())
+	if authCtx == nil {
+		http.Error(w, "Unauthorized", http.StatusUnauthorized)
+		return
+	}
+
+	// Check write permission on the resource (owner write required for metadata changes)
+	if !s.authService.CheckResourcePermission(authCtx, path, "write") {
+		http.Error(w, "Forbidden", http.StatusForbidden)
+		return
+	}
+
+	var req types.UpdateResourceMetadataRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, "Bad Request", http.StatusBadRequest)
+		return
+	}
+
+	// Get current metadata (or default if not exists)
+	currentMetadata, err := s.authService.GetResourceMetadata(path)
+	if err == badger.ErrKeyNotFound {
+		currentMetadata = &types.ResourceMetadata{
+			OwnerUUID:   authCtx.UserUUID,
+			GroupUUID:   "",
+			Permissions: types.DefaultPermissions,
+			CreatedAt:   time.Now().Unix(),
+			UpdatedAt:   time.Now().Unix(),
+		}
+	} else if err != nil {
+		s.logger.WithError(err).WithField("path", path).Error("Failed to get current resource metadata")
+		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		return
+	}
+
+	// Apply updates only to provided fields
+	updated := false
+	if req.OwnerUUID != "" {
+		currentMetadata.OwnerUUID = req.OwnerUUID
+		updated = true
+	}
+	if req.GroupUUID != "" {
+		currentMetadata.GroupUUID = req.GroupUUID
+		updated = true
+	}
+	if req.Permissions != 0 {
+		currentMetadata.Permissions = req.Permissions
+		updated = true
+	}
+	if req.TTL != "" {
+		currentMetadata.TTL = req.TTL
+		updated = true
+	}
+
+	if !updated {
+		http.Error(w, "No fields provided for update", http.StatusBadRequest)
+		return
+	}
+
+	// Store updated metadata
+	if err := s.authService.StoreResourceMetadata(path, currentMetadata); err != nil {
+		s.logger.WithError(err).WithField("path", path).Error("Failed to store resource metadata")
+		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		return
+	}
+
+	response := types.GetResourceMetadataResponse{
+		OwnerUUID:   currentMetadata.OwnerUUID,
+		GroupUUID:   currentMetadata.GroupUUID,
+		Permissions: currentMetadata.Permissions,
+		TTL:         currentMetadata.TTL,
+		CreatedAt:   currentMetadata.CreatedAt,
+		UpdatedAt:   currentMetadata.UpdatedAt,
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	json.NewEncoder(w).Encode(response)
+
+	s.logger.WithFields(logrus.Fields{
+		"path":        path,
+		"user_uuid":   authCtx.UserUUID,
+		"owner_uuid":  currentMetadata.OwnerUUID,
+		"group_uuid":  currentMetadata.GroupUUID,
+		"permissions": currentMetadata.Permissions,
+	}).Info("Resource metadata updated")
+}