Top level `make test` does not cover tests in `agent/common/*`

[thomasrutger]

The top-level make test target does not run the tests in agent/common/identityhub and agent/common/issuerservice.

The root Makefile delegates to service-specific Makefiles under agent/*, but the shared packages under agent/common/... are not covered by that structure. These packages should be added to the root test flow so make test from the repository root runs the full intended test suite.

[paullatzelsperger]

already fixed