Service Discovery: make scheme selection more intuitive in un-specified case, add more tests

[ReubenBond]

Make scheme selection more intuitive

• If ServiceDiscoveryOptions.AllowAllSchemes is TRUE and the service name INCLUDES schemes (eg https://basket), we filter out results which do not have a matching scheme, applying the preference. i.e, https+http means pick only https endpoints if any https endpoints are present, http only if no https endpoints are present.
• If ServiceDiscoveryOptions.AllowAllSchemes is TRUE and the service name DOES NOT INCLUDE schemes (eg, basket), then we should allow all endpoints.
• If ServiceDiscoveryOptions.AllowAllSchemes is FALSE, the service name DOES NOT INCLUDE schemes, and ServiceDiscoveryOptions.AllowedSchemes contains some value (eg, ["https"]), then we should filter to include only endpoints matching those AllowedSchemes values.

In pseudo code, the logic is:

IncludeAll = AllowAllSchemes && ServiceName.Schemes.Count == 0
IncludedSchemes = ServiceName.Schemes.Count > 0 ? ServiceName.Schemes.Intersect(AllowedSchemes) : AllowedSchemes

Always check "default" config section first when no endpoint name is specified

• When searching for a configuration section for a service and no endpoint name has been specified (i.e, the common case), we should first check the "default" section, then the sections corresponding to schemes. The current behavior is:
  • If the query specified any schemes, check those sections in order (https+http -> check "https" then "http" cfg sections)
  • If the query does not specify any schemes, check the "default" section.

The change is to always check the default section first if no endpoint name is specified.

Microsoft Reviewers: Open in CodeFlow

[ReubenBond]

/backport to release/8.0

[github-actions]

Started backporting to release/8.0: https://github.com/dotnet/aspire/actions/runs/8759708724