Issue title: Presence of a "@" in the login vs PersistentLogin
 Issue body: On OpenCms 9.5.2, when we use an account which have his email as login, ex: anthony50@example.com, the "reading" of the cookie seems to return an invalid token.
I suggest to replace "@" in the cookies contents by something like "_at_".
I get around this issue by registering new users with "@-replaced" email as login.
 Comments: 
 Comment 0: Fixed for release 9.5.3.
{'source': 'GithubIssues', 'repo_name_with_owner': 'alkacon/opencms-core', 'issue_id': 109328875, 'repo_stars': 547.0}