Add public API baselines to SignalR

[Pilchie]

No description provided.

[Pilchie]

Part of #24347

[dougbu]

nit: Should we craft a better Justification for the many T1 parameter, CancellationToken token = default, T2 parameter, CancellationToken token = default, … cases❔ If we were adding HubConnectionContext tomorrow, I bet we'd use the same set of overloads. Perhaps,

Suggested change

	[SuppressMessage("ApiDesign", "RS0026:Do not add multiple overloads with optional parameters", Justification = "Required to maintain compatibility")]
	[SuppressMessage("ApiDesign", "RS0026:Do not add multiple overloads with optional parameters", Justification = "May need a CancellationToken with either of these message types.")]

Of course, if you do that here, we'd need to look at the rest of our open PRs and I'm not sure it's worthwhile.

[dougbu]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[Pilchie]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[ghost]

Hello @Pilchie!

Because this pull request has the auto-merge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

p.s. you can customize the way I help with merging this pull request, such as holding this pull request until a specific person approves. Simply @mention me (@msftbot) and give me an instruction to get started! Learn more here.

[ghost]

Apologies, while this PR appears ready to be merged, it looks like release/5.0-rc2 is a protected branch and I have not been granted permission to perform the merge.