feat: add caldav tokens (#1065)

# Description

This PR adds API routes to create and manage caldav tokens. These tokens can be used instead of a user password - required for users who are using external auth providers and don't have a password.

Fixes #842

Frontend: https://kolaente.dev/vikunja/frontend/pulls/1186

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/1065

pkg/user/user_create.go

@@ -81,7 +81,7 @@ func CreateUser(s *xorm.Session, user *User) (newUser *User, err error) {
 	}
 
 	user.Status = StatusEmailConfirmationRequired
-	token, err := generateNewToken(s, user, TokenEmailConfirm)
+	token, err := generateToken(s, user, TokenEmailConfirm)
 	if err != nil {
 		return nil, err
 	}