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)

modules/validation/binding_test.go

@@ -4,24 +4,16 @@
 package validation
 
 import (
-	"net/http"
-	"net/http/httptest"
 	"testing"
 
-	"gitea.com/go-chi/binding"
-	chi "github.com/go-chi/chi/v5"
 	"github.com/stretchr/testify/assert"
 )
 
-const (
-	testRoute = "/test"
-)
-
 type (
 	validationTestCase struct {
 		description    string
 		data           any
-		expectedErrors binding.Errors
+		expectedErrors BindingErrors
 	}
 
 	TestForm struct {
@@ -33,24 +25,5 @@ type (
 )
 
 func performValidationTest(t *testing.T, testCase validationTestCase) {
-	httpRecorder := httptest.NewRecorder()
-	m := chi.NewRouter()
-
-	m.Post(testRoute, func(resp http.ResponseWriter, req *http.Request) {
-		assert.Equal(t, testCase.expectedErrors, binding.Validate(req, testCase.data))
-	})
-
-	req, err := http.NewRequest(http.MethodPost, testRoute, nil)
-	if err != nil {
-		panic(err)
-	}
-	req.Header.Add("Content-Type", "x-www-form-urlencoded")
-	m.ServeHTTP(httpRecorder, req)
-
-	switch httpRecorder.Code {
-	case http.StatusNotFound:
-		panic("Routing is messed up in test fixture (got 404): check methods and paths")
-	case http.StatusInternalServerError:
-		panic("Something bad happened on '" + testCase.description + "'")
-	}
+	assert.Equal(t, testCase.expectedErrors, Binder().Validate(t.Context(), testCase.data))
 }