EDGAR Filesystem Unit Tests

[mbfm]

We want to increase unit test coverage. EDGAR has some Setup tasks which could still benefit from more tests.

Tasks:

• [ ] WriteCaCertificate (Check+Execute; Move the check code from Execute into Check.)
• [ ] CreateServiceFile (Check; Make Check detect changes more reliably. For example, if the service user or executable path changes, it should also return TaskFulfilled::No. Maybe comparing checksums makes sense, akin to tasks::netbird::Unpack.)
• [ ] tasks::netbird::Unpack