Automate the test

[fikovnik]

It would be great to test all by:

make verify

running all the unit and integration tests in both client and server.

For the server part, it is working.
For the client it is a bit harder as we do not have a simple way start the server.
The current backend branch has server only in tests which is harder to pull into the assembled jar.

[programLyrique]

#23 is nearly ready. After merging into backend, we will have a server in the main part of the code so that it will be easier.

[fikovnik]

I think this would help a lot.

Essentially, we need a pipeline which:

• compiles the code (ideally using the devcontainer, cf. Resurect github actions for CI #26),
• runs tests (ideally with coverage, cf. Add support for codecov #25)
• runs benchmarks (ideally with Rbenchamark, cf. Add benchmarking #27)

For now I would not worry about linters...