feat(auth): password change requires old password

By checking the "old" password of the user prior to a password change, the
password change function is more secured against abuse.

Signed-off-by: Erik Michelson <github@erik.michelson.eu>

test/private-api/register-and-login.e2e-spec.ts

@@ -114,6 +114,7 @@ describe('Register and Login', () => {
       .set('Content-Type', 'application/json')
       .send(
         JSON.stringify({
+          currentPassword: PASSWORD,
           newPassword: 'newPassword',
         }),
       )