cleanup images from deleted comments

Previously, images were deleted only from comments deleted
before EditDuration expiration. After this change, any deletion
of the comment deletes images if they are not used elsewhere
in comments under the same page.

backend/_example/memory_store/server/image.go

@@ -35,7 +35,6 @@ func (s *RPC) imgResetClnTimerHndl(id uint64, params json.RawMessage) (rr jrpc.R
 	}
 	err := s.img.ResetCleanupTimer(fileID)
 	return jrpc.EncodeResponse(id, nil, err)
-
 }
 
 func (s *RPC) imgLoadHndl(id uint64, params json.RawMessage) (rr jrpc.Response) {
@@ -47,6 +46,16 @@ func (s *RPC) imgLoadHndl(id uint64, params json.RawMessage) (rr jrpc.Response)
 	return jrpc.EncodeResponse(id, value, err)
 }
 
+func (s *RPC) imgDeleteHndl(id uint64, params json.RawMessage) (rr jrpc.Response) {
+	var fileID string
+	if err := json.Unmarshal(params, &fileID); err != nil {
+		return jrpc.Response{Error: err.Error()}
+	}
+	err := s.img.Delete(fileID)
+	return jrpc.EncodeResponse(id, nil, err)
+
+}
+
 func (s *RPC) imgCommitHndl(id uint64, params json.RawMessage) (rr jrpc.Response) {
 	var fileID string
 	if err := json.Unmarshal(params, &fileID); err != nil {

backend/_example/memory_store/server/image_test.go

@@ -158,4 +158,9 @@ func TestRPC_imgInfoHndl(t *testing.T) {
 	info, err = ri.Info()
 	assert.NoError(t, err)
 	assert.False(t, info.FirstStagingImageTS.IsZero())
+
+	err = ri.Delete("test_img")
+	assert.NoError(t, err)
+	_, err = ri.Load("test_img")
+	assert.EqualError(t, err, "image test_img not found")
 }

backend/_example/memory_store/server/rpc.go

@@ -60,6 +60,7 @@ func (s *RPC) addHandlers() {
 		"save_with_id":        s.imgSaveWithIDHndl,
 		"reset_cleanup_timer": s.imgResetClnTimerHndl,
 		"load":                s.imgLoadHndl,
+		"delete":              s.imgDeleteHndl,
 		"commit":              s.imgCommitHndl,
 		"cleanup":             s.imgCleanupHndl,
 		"info":                s.imgInfoHndl,