pcluster dcv fails when username contains dot

[ezrizhu]

https://github.com/aws/aws-parallelcluster-cookbook/blob/develop/cookbooks/aws-parallelcluster-platform/files/dcv/pcluster_dcv_authenticator.py#L136
above line is not allowing usernames with . (dot) in their username to create a dcv session.
dots are usually permitted in AD/LDAP environments- and pcluster claims compatability with AD/LDAP via https://docs.aws.amazon.com/parallelcluster/latest/ug/tutorials_05_multi-user-ad.html

[ezrizhu]

we resolved this in our deployment with sed -i 's/a-z0-9_-/a-z0-9_.-/g' /home/dcvextauth/pcluster_dcv_authenticator.py then a /opt/parallelcluster/pyenv/versions/3.14.2/envs/cookbook_virtualenv/bin/supervisorctl restart pcluster_dcv_authenticator as a bootstrap script hook