Add support for Maven buildsystem.

[sebastic]

As reported on the Debian GIS mailinglist, the switch to gradle 8.x broke the osmosis Debian package build because gradle is stuck at 4.4. It's nearly impossible to package recent gradle releases due to its use of kotlin which in turn depends on ancient JREs. Fedora has removed their gradle package entirely because it's unmaintainable for example.

This PR adds support for Maven to build the JARs. This helps packagers keep osmosis in their distribution.

I haven't found a good replacement for the gradle application plugin to create the launcher, so I've reverted back to plexus in the Debian package. We should likely move those changes back into the osmosis repo as well.

[brettch]

Hi @sebastic. This sounds like a frustrating situation.

I'm very hesitant to merge this myself. Osmosis is barely supported as it is and this will make it even more unlikely that new releases will get published. I'd really like to step away completely but I try to keep the lights on for those that still use it. If any volunteers want to take on maintenance of Osmosis it might change things.

[sebastic]

I'll be maintaining the Maven buildsystem for the sake of the Debian package anyway.

We mostly need to bump the dependency versions in both gradle.properties and the parent pom.xml going forward. And run sed -i 's@<version>old</version>@<version>new</version> pom.xml */pom.xml on release, I haven't found a way to set that dynamically.

[sebastic]

I'm not sure if I will keep updating my maven branch for new Osmosis releases.

The most recent version of these changes can be found in the Debian package repo:

https://salsa.debian.org/debian-gis-team/osmosis/-/blob/master/debian/patches/maven.patch