Refactor locale&string&template related code (#29165)

Clarify when "string" should be used (and be escaped), and when
"template.HTML" should be used (no need to escape)

And help PRs like  #29059 , to render the error messages correctly.

(cherry picked from commit f3eb835886031df7a562abc123c3f6011c81eca8)

Conflicts:
	modules/web/middleware/binding.go
	routers/web/feed/convert.go
	tests/integration/branches_test.go
	tests/integration/repo_branch_test.go
	trivial context conflicts

modules/context/context.go

@@ -6,7 +6,7 @@ package context
 
 import (
 	"context"
-	"html"
+	"fmt"
 	"html/template"
 	"io"
 	"net/http"
@@ -71,16 +71,6 @@ func init() {
 	})
 }
 
-// TrHTMLEscapeArgs runs ".Locale.Tr()" but pre-escapes all arguments with html.EscapeString.
-// This is useful if the locale message is intended to only produce HTML content.
-func (ctx *Context) TrHTMLEscapeArgs(msg string, args ...string) string {
-	trArgs := make([]any, len(args))
-	for i, arg := range args {
-		trArgs[i] = html.EscapeString(arg)
-	}
-	return ctx.Locale.Tr(msg, trArgs...)
-}
-
 type webContextKeyType struct{}
 
 var WebContextKey = webContextKeyType{}
@@ -253,6 +243,13 @@ func (ctx *Context) JSONOK() {
 	ctx.JSON(http.StatusOK, map[string]any{"ok": true}) // this is only a dummy response, frontend seldom uses it
 }
 
-func (ctx *Context) JSONError(msg string) {
-	ctx.JSON(http.StatusBadRequest, map[string]any{"errorMessage": msg})
+func (ctx *Context) JSONError(msg any) {
+	switch v := msg.(type) {
+	case string:
+		ctx.JSON(http.StatusBadRequest, map[string]any{"errorMessage": v, "renderFormat": "text"})
+	case template.HTML:
+		ctx.JSON(http.StatusBadRequest, map[string]any{"errorMessage": v, "renderFormat": "html"})
+	default:
+		panic(fmt.Sprintf("unsupported type: %T", msg))
+	}
 }