Add CassandraDb HealthCheck support

[djesusnet]

What this PR does / why we need it: Adds health check support for CassandraDb

Does this PR introduce a user-facing change?: It adds a new package to support CassandraDb health checks

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Unit tests passing
• End-to-end tests passing
• Extended the documentation
• Provided sample for the feature

[djesusnet]

@dotnet-policy-service agree

[djesusnet]

@esskar @manne @Daniel15 @inkel , Could you please review this PR when you have some time?

[inkel]

I'd love to! But I haven't written any .NET code in years, and I'm not a maintainer of this project, sorry. FWIW the code LGTM.

[djesusnet]

@sungam3r Could you review my PR?

[adamsitnik]

Overall it's welcomed and high quality contribution. Thank you @djesusnet !

We need to agree on the shape of the API. Please see my comment and let me know what you think about it.

[adamsitnik]

With the current approach, we would build a new instance every time the health check would be invoked. Which I expect would be bad for performance and could even lead to some resource leaks (nothing is getting disposed here).

We have changed many of our health checks similar to what I described in #2040: for all the client instances that are thread-safe and should be used as singleton, we don't create our own instances, but expect it to be resolved from the DI (so the user registers a singleton and we just resolve).

I've done some quick web search, but have failed to find dependency injection best practices for working with the C# client of CassandarDb.

Should we just expect the users to inject the cluster into the DI and solve it?

For example this is what we do for MongoDB:

We allow the users to specify a Func<IServiceProvider, IMongoClient> factory:

AspNetCore.Diagnostics.HealthChecks/src/HealthChecks.MongoDb/DependencyInjection/MongoDbHealthCheckBuilderExtensions.cs

Line 33 in 36bf171

Func<IServiceProvider, IMongoClient>? clientFactory = default,

when it's not specified, we just try to resolve it from the DI container:

AspNetCore.Diagnostics.HealthChecks/src/HealthChecks.MongoDb/DependencyInjection/MongoDbHealthCheckBuilderExtensions.cs

Line 51 in 36bf171

IMongoClient client = clientFactory?.Invoke(sp) ?? sp.GetService<MongoClient>() ?? sp.GetRequiredService<IMongoClient>();