Expand Namespace character support

[TohnJhomas]

A spark integration is automatically creating the namespace abfss://root@datalakedev.dfs.core.windows.net for a user, despite the @ symbol not being supported in namespaces.

As a result, the api is sending 400 errors in response to runEvents.

We should look into expanding to support a broader character set in order to head off these issues in the future. In the immediate sense, we at least need to support the @ symbol to get this user unstuck.

This user has created an alias in the interim, but aren't able to fully resolve the problem without editing the spark integration

[darezik]

This also appears to be the root cause for #1793

[wslulciuc]

Fixed #1925

[gage-russell]

@wslulciuc Why was this closed?

#1925 addresses maximum length of 1024 characters.

But the issue is that @ is not included in the regex check for namespace.