Start using template context function (#26254)

Before:

* `{{.locale.Tr ...}}`
* `{{$.locale.Tr ...}}`
* `{{$.root.locale.Tr ...}}`
* `{{template "sub" .}}`
* `{{template "sub" (dict "locale" $.locale)}}`
* `{{template "sub" (dict "root" $)}}`
* .....

With context function: only need to `{{ctx.Locale.Tr ...}}`

The "ctx" could be considered as a super-global variable for all
templates including sub-templates.


To avoid potential risks (any bug in the template context function
package), this PR only starts using "ctx" in "head.tmpl" and
"footer.tmpl" and it has a "DataRaceCheck". If there is anything wrong,
the code can be fixed or reverted easily.

modules/templates/htmlrenderer.go

@@ -6,6 +6,7 @@ package templates
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -39,27 +40,28 @@ var (
 
 var ErrTemplateNotInitialized = errors.New("template system is not initialized, check your log for errors")
 
-func (h *HTMLRender) HTML(w io.Writer, status int, name string, data any) error {
+func (h *HTMLRender) HTML(w io.Writer, status int, name string, data any, ctx context.Context) error { //nolint:revive
 	if respWriter, ok := w.(http.ResponseWriter); ok {
 		if respWriter.Header().Get("Content-Type") == "" {
 			respWriter.Header().Set("Content-Type", "text/html; charset=utf-8")
 		}
 		respWriter.WriteHeader(status)
 	}
-	t, err := h.TemplateLookup(name)
+	t, err := h.TemplateLookup(name, ctx)
 	if err != nil {
 		return texttemplate.ExecError{Name: name, Err: err}
 	}
 	return t.Execute(w, data)
 }
 
-func (h *HTMLRender) TemplateLookup(name string) (TemplateExecutor, error) {
+func (h *HTMLRender) TemplateLookup(name string, ctx context.Context) (TemplateExecutor, error) { //nolint:revive
 	tmpls := h.templates.Load()
 	if tmpls == nil {
 		return nil, ErrTemplateNotInitialized
 	}
-
-	return tmpls.Executor(name, NewFuncMap())
+	m := NewFuncMap()
+	m["ctx"] = func() any { return ctx }
+	return tmpls.Executor(name, m)
 }
 
 func (h *HTMLRender) CompileTemplates() error {