[F3] promote F3 users to matching OAuth2 users on first sign-in

(cherry picked from commit bd7fef7496)

services/auth/source/f3/source.go

@@ -0,0 +1,33 @@
+// SPDX-FileCopyrightText: Copyright the Forgejo contributors
+// SPDX-License-Identifier: MIT
+
+package f3
+
+import (
+	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/modules/json"
+)
+
+type Source struct {
+	URL            string
+	MatchingSource string
+
+	// reference to the authSource
+	authSource *auth.Source
+}
+
+func (source *Source) FromDB(bs []byte) error {
+	return json.UnmarshalHandleDoubleEncode(bs, &source)
+}
+
+func (source *Source) ToDB() ([]byte, error) {
+	return json.Marshal(source)
+}
+
+func (source *Source) SetAuthSource(authSource *auth.Source) {
+	source.authSource = authSource
+}
+
+func init() {
+	auth.RegisterTypeConfig(auth.F3, &Source{})
+}