refactor: http request binding (#38971)

Better than before, still not good enough (more work can be done in the
future)

And add the missing error handling in the PrivateContext "bind"
middleware.

By the way, picked some "TrimSpace" changes from "fix: trim whitespace
from SMTP address and port - #38934" (fix #38926)

services/context/context.go

@@ -23,11 +23,10 @@ import (
 	"gitea.dev/modules/templates"
 	"gitea.dev/modules/translation"
 	"gitea.dev/modules/util"
+	"gitea.dev/modules/validation"
 	"gitea.dev/modules/web"
 	"gitea.dev/modules/web/middleware"
 	web_types "gitea.dev/modules/web/types"
-
-	"gitea.com/go-chi/binding"
 )
 
 // Render represents a template render
@@ -83,28 +82,6 @@ func GetWebContext(ctx context.Context) *Context {
 	return webCtx
 }
 
-// GetValidateContext gets a context for middleware form validation
-func GetValidateContext(req *http.Request) (ctx *middleware.ValidateContext) {
-	if ctxAPI, ok := req.Context().Value(apiContextKey).(*APIContext); ok {
-		ctx = &middleware.ValidateContext{
-			Data:   ctxAPI.Data,
-			Locale: ctxAPI.Locale,
-			Req:    ctxAPI.Req,
-			Resp:   ctxAPI.Resp,
-		}
-	} else if ctxWeb, ok := req.Context().Value(WebContextKey).(*Context); ok {
-		ctx = &middleware.ValidateContext{
-			Data:   ctxWeb.Data,
-			Locale: ctxWeb.Locale,
-			Req:    ctxWeb.Req,
-			Resp:   ctxWeb.Resp,
-		}
-	} else {
-		panic("invalid context, expect either APIContext or Context")
-	}
-	return ctx
-}
-
 func NewTemplateContextForWeb(ctx reqctx.RequestContext, req *http.Request, locale translation.Locale) TemplateContext {
 	tmplCtx := NewTemplateContext(ctx, req)
 	tmplCtx["Locale"] = locale
@@ -294,21 +271,16 @@ func (ctx *Context) JSONErrorNotFound(optMsg ...string) {
 	ctx.JSON(http.StatusNotFound, buildJsonErrorMap(msg))
 }
 
-func GetFetchActionForm[T interface {
-	*E
-	middleware.Form
-}, E any](ctx *Context) *E {
+func GetFetchActionForm[T middleware.Form](ctx *Context) (ret T) {
 	if web.IsFormSet(ctx) {
 		panic("don't mix fetch-action form validation with template-based form validation")
 	}
-	form := T(new(E))
-	errs := binding.Bind(ctx.Req, form)
-	errs = form.Validate(GetValidateContext(ctx.Req), errs)
+	form, errs := middleware.BindFormValidate[T](ctx.Req, validation.Binder())
 	errorMessage, fieldName, _ := middleware.BuildValidationErrorForUser(form, ctx.Locale, errs)
 	if errorMessage != "" {
 		ctx.Resp.Header().Set("Content-Type", "application/json")
 		ctx.JSONErrorWithField(errorMessage, fieldName)
-		return nil
+		return ret
 	}
 	return form
 }