Add templates for Aspire test projects

[DamianEdwards]

Adds an option to the Aspire Starter App solution template for creating a tests project, as well as a new standalone Aspire tests project template.

Fixes #579

Microsoft Reviewers: Open in CodeFlow

[phenning]

Damian, let’s talk next week if we want to consider detecting if the integration test template is installed at initial project creation and giving an option in NPD to create it then. We could set the reference and IVT upfront at project creation. In anticipation of this, we might want to consider an option to suppress outputting the instructional text.

[DamianEdwards]

@phenning thanks, I've logged #2924 to follow up.

[eerhardt]

Just a couple minor comments. This looks good to me. Thanks!

[eerhardt]

A nice thing we do in our tests is:

aspire/tests/Aspire.EndToEnd.Tests/IntegrationServicesTests.cs

Lines 38 to 41 in 9073e07

	var response = await _integrationServicesFixture.IntegrationServiceA.HttpGetAsync("http", $"/{resourceName}/verify");
	var responseContent = await response.Content.ReadAsStringAsync();
	Assert.True(response.IsSuccessStatusCode, responseContent);

That way if it fails, you get the responseContent logged.

[DamianEdwards]

Because we have resiliency on the HttpClient returned from CreateHttpClient, you can't actually do it quite like that, as if the status code wasn't a success status code, it will retry until it fails anyway. I think keeping this test in the template simple is probably best for now.

[eerhardt]

Doesn't resilience only retry on certain failures? If a service returns 500 (Internal Server Error), it wouldn't retry that, would it?

[DamianEdwards]

Actually I'm not sure, I thought a 500 is exactly the kind of thing it would retry, vs. a 300 or 400 status code. Obviously connection level issues would be retried too.