Refactor secrets modification logic (#26873)

- Share code between web and api
- Add some tests

services/secrets/validation.go

@@ -0,0 +1,25 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package secrets
+
+import (
+	"regexp"
+
+	"code.gitea.io/gitea/modules/util"
+)
+
+// https://docs.github.com/en/actions/security-guides/encrypted-secrets#naming-your-secrets
+var (
+	namePattern            = regexp.MustCompile("(?i)^[A-Z_][A-Z0-9_]*$")
+	forbiddenPrefixPattern = regexp.MustCompile("(?i)^GIT(EA|HUB)_")
+
+	ErrInvalidName = util.NewInvalidArgumentErrorf("invalid secret name")
+)
+
+func ValidateName(name string) error {
+	if !namePattern.MatchString(name) || forbiddenPrefixPattern.MatchString(name) {
+		return ErrInvalidName
+	}
+	return nil
+}