Adding upstream version 0.8.9.

Signed-off-by: Daniel Baumann <daniel@debian.org>

pkg/services/smtp/smtp_oauth2.go

@@ -0,0 +1,25 @@
+package smtp
+
+import (
+	"net/smtp"
+)
+
+type oauth2Auth struct {
+	username, accessToken string
+}
+
+// OAuth2Auth returns an Auth that implements the SASL XOAUTH2 authentication
+// as per https://developers.google.com/gmail/imap/xoauth2-protocol
+func OAuth2Auth(username, accessToken string) smtp.Auth {
+	return &oauth2Auth{username, accessToken}
+}
+
+func (a *oauth2Auth) Start(_ *smtp.ServerInfo) (string, []byte, error) {
+	resp := []byte("user=" + a.username + "\x01auth=Bearer " + a.accessToken + "\x01\x01")
+
+	return "XOAUTH2", resp, nil
+}
+
+func (a *oauth2Auth) Next(_ []byte, _ bool) ([]byte, error) {
+	return nil, nil
+}