Regex/wildcard filters for include/exclude

[Unmoon]

Is your feature request related to a problem? Please describe.
I want to protect my users from dependency confusion attacks (malicious or accidental).

Describe the solution you'd like
I want to exclude packages in specific namespace (for example google for google-this and google-that) from repository pull-through caching.

Describe alternatives you've considered
Requiring user to configure two repositories where one takes priority.

Additional context
Somewhat related to #998

Repository pull-through sample in #1004

https://matrix.to/#/!ddcyhqxyFqGMoDLDeP:matrix.org/$5kmR0IyrQ0IQCGq9BHvRskUhB0UJROnZ-sISpgokVSA?via=matrix.org&via=ctrl-c.liu.se&via=x9c4.spdns.org