Cleanup tests on the server side

# Cleanup tests on the server side

## Context

The server side has 3 kind of tests :
* Unit tests
* Integration Tests
* Mutation Tests

The mutation & integration tests are clearly the parts that take most of the time in a full build. We can go through 30min of build just with them.

# Expected
* Cleanup the pom.xml of the useless dependencies and declarations for tests.
* Try to optimize PITest execution time, and if not possible, challenge other solutions that this.
* Try to optimize the integration tests by creating a temporary server instance for all of them and not one instance / integration test.

Start by reviewing pom.xml and mapping the declared test dependencies and configurations to the unit, integration, and mutation test commands. Measure PITest and integration-test execution, then compare results after removing unused declarations or reusing a temporary server instance; done means shorter builds without losing test coverage.

Written by the indexing model from the issue text.