Make optional.Option[T] type serializable (#29282)

make the generic `Option` type de-/serializable for json and yaml

---------

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
(cherry picked from commit 53c7d8908e5ef35818b72b8c3d873b509269bc1a)

modules/optional/serialization.go

@@ -0,0 +1,46 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package optional
+
+import (
+	"code.gitea.io/gitea/modules/json"
+
+	"gopkg.in/yaml.v3"
+)
+
+func (o *Option[T]) UnmarshalJSON(data []byte) error {
+	var v *T
+	if err := json.Unmarshal(data, &v); err != nil {
+		return err
+	}
+	*o = FromPtr(v)
+	return nil
+}
+
+func (o Option[T]) MarshalJSON() ([]byte, error) {
+	if !o.Has() {
+		return []byte("null"), nil
+	}
+
+	return json.Marshal(o.Value())
+}
+
+func (o *Option[T]) UnmarshalYAML(value *yaml.Node) error {
+	var v *T
+	if err := value.Decode(&v); err != nil {
+		return err
+	}
+	*o = FromPtr(v)
+	return nil
+}
+
+func (o Option[T]) MarshalYAML() (interface{}, error) {
+	if !o.Has() {
+		return nil, nil
+	}
+
+	value := new(yaml.Node)
+	err := value.Encode(o.Value())
+	return value, err
+}