Chore: Move remaining web framework code to pkg/web, remove macaron binding module (#43018)

* remove macaron binding dependency

* completely purge macaron binding

* move everything to pkg/web

* remove non-go files from pkg/web

* clean up leftovers of macaron imports

* make linter happy

pkg/web/render.go

@@ -0,0 +1,72 @@
+// Copyright 2013 Martini Authors
+// Copyright 2014 The Macaron Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"): you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+
+package web
+
+import (
+	"html/template"
+	"io/fs"
+	"net/http"
+	"os"
+	"path/filepath"
+)
+
+// Renderer is a Middleware that injects a template renderer into the macaron context, enabling ctx.HTML calls in the handlers.
+// If MACARON_ENV is set to "development" then templates will be recompiled on every request. For more performance, set the
+// MACARON_ENV environment variable to "production".
+func Renderer(dir, leftDelim, rightDelim string) func(http.Handler) http.Handler {
+	fs := os.DirFS(dir)
+	t, err := compileTemplates(fs, leftDelim, rightDelim)
+	if err != nil {
+		panic("Renderer: " + err.Error())
+	}
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+			ctx := FromContext(req.Context())
+			if Env == DEV {
+				if t, err = compileTemplates(fs, leftDelim, rightDelim); err != nil {
+					panic("Context.HTML:" + err.Error())
+				}
+			}
+			ctx.template = t
+			next.ServeHTTP(rw, req)
+		})
+	}
+}
+
+func compileTemplates(filesystem fs.FS, leftDelim, rightDelim string) (*template.Template, error) {
+	t := template.New("")
+	t.Delims(leftDelim, rightDelim)
+	err := fs.WalkDir(filesystem, ".", func(path string, d fs.DirEntry, e error) error {
+		if e != nil {
+			return nil // skip unreadable or erroneous filesystem items
+		}
+		if d.IsDir() {
+			return nil
+		}
+		ext := filepath.Ext(path)
+		if ext != ".html" && ext != ".tmpl" {
+			return nil
+		}
+		data, err := fs.ReadFile(filesystem, path)
+		if err != nil {
+			return err
+		}
+		basename := path[:len(path)-len(ext)]
+		_, err = t.New(basename).Parse(string(data))
+		return err
+	})
+	return t, err
+}