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/regex_pattern_test.go

@@ -6,8 +6,6 @@ package validation
 import (
 	"regexp"
 	"testing"
-
-	"gitea.com/go-chi/binding"
 )
 
 func getRegexPatternErrorString(pattern string) string {
@@ -18,29 +16,27 @@ func getRegexPatternErrorString(pattern string) string {
 }
 
 func Test_RegexPatternValidation(t *testing.T) {
-	AddBindingRules()
-
 	regexValidationTestCases := []validationTestCase{
 		{
 			description: "Empty regex pattern",
-			data: TestForm{
+			data: &TestForm{
 				RegexPattern: "",
 			},
 		},
 		{
 			description: "Valid regex",
-			data: TestForm{
+			data: &TestForm{
 				RegexPattern: `(\d{1,3})+`,
 			},
 		},
 
 		{
 			description: "Invalid regex",
-			data: TestForm{
+			data: &TestForm{
 				RegexPattern: "[a-",
 			},
-			expectedErrors: binding.Errors{
-				binding.Error{
+			expectedErrors: BindingErrors{
+				BindingError{
 					FieldNames:     []string{"RegexPattern"},
 					Classification: ErrRegexPattern,
 					Message:        getRegexPatternErrorString("[a-"),