support Nextcloud OAuth 2.0 authentication

pkg/auth/oauth2/oauth2_user_info.go

@@ -0,0 +1,13 @@
+package oauth2
+
+import "github.com/mayswind/ezbookkeeping/pkg/core"
+
+// OAuth2UserInfo represents the user info retrieved from OAuth 2.0 provider
+type OAuth2UserInfo struct {
+	UserName       string
+	Email          string
+	NickName       string
+	LanguageCode   string
+	CurrencyCode   string
+	FirstDayOfWeek core.WeekDay
+}