Allow '.' in usernames

[buminks]

Allow '.' in a username as valid character in exclude username filter.

The same kind of change was done in #233.

Testing done

mvn verify is running without errors.

before the change:

after the change:

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[Eccenux]

+1 from me.

It should work with basic auth which is implemented in (dot should work in any encoding):
svnkit\src\main\java\org\tmatesoft\svn\core\internal\io\dav\http\HTTPBasicAuthentication.java

Fine in NTLM too
https://learn.microsoft.com/en-us/previous-versions//cc722458(v=technet.10)?redirectedfrom=MSDN

User names cannot contain certain characters. Invalid characters include:
" / \ [ ] : ; | = , + * ? < >
User names can contain all other special characters, including spaces, periods, dashes, and underscores. But it's generally not a good idea to use spaces in account names.

[Eccenux]

OK

[buminks]

@Eccenux Thanks for your support.