Split "modules/context.go" to separate files (#24569)

The "modules/context.go" is too large to maintain.

This PR splits it to separate files, eg: context_request.go,
context_response.go, context_serve.go

This PR will help:

1. The future refactoring for Gitea's web context (eg: simplify the context)
2. Introduce proper "range request" support
3. Introduce context function

This PR only moves code, doesn't change any logic.

modules/context/context_request.go

@@ -0,0 +1,59 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package context
+
+import (
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/go-chi/chi/v5"
+)
+
+// RemoteAddr returns the client machine ip address
+func (ctx *Context) RemoteAddr() string {
+	return ctx.Req.RemoteAddr
+}
+
+// Params returns the param on route
+func (ctx *Context) Params(p string) string {
+	s, _ := url.PathUnescape(chi.URLParam(ctx.Req, strings.TrimPrefix(p, ":")))
+	return s
+}
+
+// ParamsInt64 returns the param on route as int64
+func (ctx *Context) ParamsInt64(p string) int64 {
+	v, _ := strconv.ParseInt(ctx.Params(p), 10, 64)
+	return v
+}
+
+// SetParams set params into routes
+func (ctx *Context) SetParams(k, v string) {
+	chiCtx := chi.RouteContext(ctx)
+	chiCtx.URLParams.Add(strings.TrimPrefix(k, ":"), url.PathEscape(v))
+}
+
+// UploadStream returns the request body or the first form file
+// Only form files need to get closed.
+func (ctx *Context) UploadStream() (rd io.ReadCloser, needToClose bool, err error) {
+	contentType := strings.ToLower(ctx.Req.Header.Get("Content-Type"))
+	if strings.HasPrefix(contentType, "application/x-www-form-urlencoded") || strings.HasPrefix(contentType, "multipart/form-data") {
+		if err := ctx.Req.ParseMultipartForm(32 << 20); err != nil {
+			return nil, false, err
+		}
+		if ctx.Req.MultipartForm.File == nil {
+			return nil, false, http.ErrMissingFile
+		}
+		for _, files := range ctx.Req.MultipartForm.File {
+			if len(files) > 0 {
+				r, err := files[0].Open()
+				return r, true, err
+			}
+		}
+		return nil, false, http.ErrMissingFile
+	}
+	return ctx.Req.Body, false, nil
+}