Make SyncFixture users use seperate directories and clean them up

[myieye]

It seemed to me that the Directory.Delete calls in InitializeAsync were trying to delete files being used by other tests (and causing failures for me). So, I've adapted the Fixture to use a different directory per SyncFixture. That means we don't know how to clean up old test projects on start, so I'm cleaning them up at the end.

It took me a while to figure out how to close pooled open connections. Largely, because there are 3 different SqliteConnection classes to choose from and they all have ClearAllPools(), but I overlooked the 3rd one and that's the one I actually needed 😆.

It also not clear to me how we'd only clear the connections to just a single db if we wanted to delete it in e.g. prod.

For a while I thought that the db file was still in use after the tests, because CrdtProjectsService.CreateProject() has var db = serviceScope.ServiceProvider.GetRequiredService<LcmCrdtDbContext>(); and doesn't dispose the db afterwards. But disposing it didn't help. And I believe that DbContext will get disposed at the end of the current scope?

[hahn-kev]

I've found the most reliable way to cleanup a db is to use DbContext.Database.EnsureDeleted(). That said I would prefer if we could maintain the current functionality where it cleans up at the start. I think we can get the best of both worlds though by using a singleton to track if we've already done our cleanup. So in InitializeAsync we try to delete the projects from the previous test run, right now we do that every time a SyncFixture is created (causing the issue you are trying to fix), what if we only did that cleanup once using a static bool to track that? We would need to us a lock to avoid race conditions.

[myieye]

I've changed it to only clean up on start again

[hahn-kev]

Looks good to me, I might use a HashSet instead of a dictionary considering we never read the value, but it doesn't matter here.