chore: improved Dockerfile to utilize cached layers

[mxzinke]

It was kind of annoying to me, doing a complete refetch of the dependencies on each build within docker.

[wipfli]

@bdon do we actually want to keep maintaining this dockerfile?

[wipfli]

Thanks for opening the pull request in any case @mxzinke. I just never used that file before and maybe we could abandon docker for the build altogether...

[mxzinke]

I am a big fan of Docker, since it makes it easier for me to jump between projects without messing around with dependencies.

In my opinion, it's a must-have for open-source project and if there were no before, I did not even look deeper into the project since no JDK whatsoever is installed on my computer. Basically, for everyone coming to the project, they can go build the docker image and take a test run.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[bdon]

Thanks, this is a nice improvement but it still looks like it contacts the repository at mvn clean package step without the -o flag? (I couldn't get that to work)

I think we should have a Dockerfile for the audience that prefers that, though to make this a good experience we would also need to provide some instructions around mounting the data directory volume from the host so it doesn't re-download sources every time.