feat: add support for using custom .m2 directory

[agdimech]

The existing Java packaging process uses a localRepository which points to a newly created tmp directory. This means that when building, all dependencies need to be freshly downloaded which is contributing a significant portion of time to the packaging process.

This PR provides the option to the user (hidden) to use a non-transient .m2 local repository if they so choose. I have experienced a huge improvement to performance by enabling this setting (5s with enabled vs 4 minutes using defaults).

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[agdimech]

I have set the default to false for this setting to maintain backward compatibility. I am wandering whether this should be defaulted to true in future as I am not sure what negative side effects there would be by using the user's .m2 repository.

[RomainMuller]

We moved away from the default cache locations for both .NET and Java because this had surprising consequences due to how both will always prefer artifacts already in cache (which is good), AND store the outputs of local builds into this cache (which is where surprises come from).

I reckon the performance improvement you see comes from not re-downloading dependencies on each build... which is also achieved when using a non-default, but also non-transient cache. Maybe the right think is to allow configuring a specific .m2 directory (which could be the default one, if that is what the user wants). This would be more flexible and also feels safer...

[RomainMuller]

Can you perhaps also see to use that configuration flag somewhere (e.g: in one of the flavors of the build test, perhaps)?

Pull request has been modified.

[mergify]

Thank you for contributing! ❤️ I will now look into making sure the PR is up-to-date, then proceed to try and merge it!

[mergify]

Merging (with squash)...

[mergify]

Merging (with squash)...

[mergify]

Merging (with squash)...