experiment: prototyping new ASP.NET-like controllers;

feat: ControllerMethod struct for storing data about an individual API endpoint;
feat: controllerImpl struct for setting up a controller;
feat: GetRequest method for parsing and validating a request with automatic abortion on binding/validation errors

backend/internal/errors/controller.go

@@ -0,0 +1,24 @@
+// Copyright (c) 2025 Nikolai Papin
+//
+// This file is part of Easywish
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+// the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package errors
+
+import "errors"
+
+var (
+	ErrClientInfoNotProvided = errors.New("No client info provded")
+)