Make SignalR Service usage an aspect of deployment, not source code

[SteveSandersonMS]

For Razor Components (currently, server-side Blazor), the decision to use Azure SignalR Service or not shouldn't be hardcoded into the app code. Ideally it would be something determined by the deployment mechanism.

Somehow we need sufficient abstraction to remove this from the project source code. The tricky bit is that we don't want to bring in a dependency on Microsoft.Azure.SignalR for all projects, so I'm not sure how we solve this.

I seem to recall that @DamianEdwards mentioned this is just a one example of a broader class of requirements to make service usage determined by the deployment/hosting mechanism. So perhaps this is not something we need to solve in this repo, because we're going to inherit a broader solution that applies to all services. CC @davidfowl.

[davidfowl]

cc @anurse @bradygaster Something we need to change in SignalR itself.

[bradygaster]

Precisely my thinking when i invited the tooling team to our original discussion, as they'll eventually need to be involved. What i don't know [yet] is if we also need to involve someone on the Kudu and/or Azure DevOps sides. I will begin to find out now, so we're prepared. Also we should factor this into our considerations for the 3.0 milestone.

[rynowak]

@davidfowl - I know you're working on this - is there another item that tracks this?