Add support for Maven repositories

:white_check_mark: Checklist

[x] I have searched open and closed issues for duplicates.
[x] This is a request for a new feature in the Data Safe Haven or an upgrade to an existing feature.
[x] The feature is still missing in the latest version.
[x] I have read through the documentation.
[x] This isn't an open-ended question (open a discussion if it is).

We should support Maven as a repository source.