add project groups to frontend.

api/project.go

@@ -62,6 +62,10 @@ func Project(g *gin.RouterGroup, db database.Database) {
 		project.UserID = auth.UserID(c)
 		project.CreatedTime = time.Now().UTC()
 
+		if project.GroupID != nil && *project.GroupID == "" {
+			project.GroupID = nil
+		}
+
 		err = db.Projects().Insert(c.Request.Context(), project)
 		if err != nil {
 			return nil, err