zfr authentication adapter did not verify validity of tokens
Previous to @2ca5bb1c2f11537be8f94ca6867d8d69789e744a (release [0.1.2](https://github.com/zf-fr/zfr-oauth2-server-module/tree/0.1.2)), tokens weren't checked for validity/expiration.
This potentially caused a security issue if expired tokens were not deleted after the expiration time was past, allowing anyone to still use invalidated authentication credentials.