Login: handle custom token creation error messages (#31283)

* Login: handle custom token creation errors

* Login: handle external error for OAuth responses

pkg/models/user_token.go

@@ -11,6 +11,20 @@ var (
 	ErrUserTokenNotFound = errors.New("user token not found")
 )
 
+// CreateTokenErr represents a token creation error; used in Enterprise
+type CreateTokenErr struct {
+	StatusCode  int
+	InternalErr error
+	ExternalErr string
+}
+
+func (e *CreateTokenErr) Error() string {
+	if e.InternalErr != nil {
+		return e.InternalErr.Error()
+	}
+	return "failed to create token"
+}
+
 type TokenExpiredError struct {
 	UserID  int64
 	TokenID int64