Unsubscribe from redis topic async

[dannyheard7]

Summary of the changes (Less than 80 chars)

Changes DefaultTopic.OnConnectAsync to return IAsyncDisposable instead of IDisposable (breaking) so that RedisTopic can unsubscribe asynchronously

Closes #8199

[dannyheard7]

CONTRIBUTING.md mentions updating the unshipped public api text file, however I can't find this in the repository - if you let me know what needs updating instead then I'll do that

[michaelstaib]

can you have a look at this PR and amend yours so that its not a breaking change?

#8202

[dannyheard7]

@michaelstaib Any idea when we could see this merged in / released? We are seeing this cause performance issues in our server

[michaelstaib]

@dannyheard7 the test still fails.

[dannyheard7]

Ok i've removed the test as I can't think of a better way to test this and the mock seems flaky on the build server

[michaelstaib]

Without test we cannot merge it ... we need to verify your change.

[michaelstaib]

You have forked in a way that we cannot push changes into this PR ... we can take over the PR but than you loose your credits.

[michaelstaib]

There are three things that need to be tested ...

1. If you are not implementing IAsyncDisposable the standard dispose is triggered.
2. If you are implementing IAsyncDisposable the async dispose is triggered.

These two cover the change in the DefaultTopic.

3. You need to verify that the DisposeAsync works correctly on the RedisTopic you can also use squadron and there is no need to mock.

[michaelstaib]

This looks good