[13.2] Document new contextual endpoint resolution apis.

@IEvangelist is already working on this.

Since Feb 5, 2026.

You can now resolve endpoints from the perspective of specific resources. Depending on your ocnext, the same resource could be `http://host.docker.internal:1234`, `http://localhost:1234` or `http://resource.dev.internal:4567` depending on where you resolved it from.

```cs
var endpoint = redis.GetEndpoint("tcp")
var url = await endpoint.GetValueAsync(new ValueProviderContext {
Caller = containerApp.Resource,
});
```

You can also resolve the url from the perspective of a specific network:

```cs
var endpoint = redis.GetEndpoint("tcp")
var url = await endpoint.GetValueAsync(new ValueProviderContext {
Network = KnownNetworkIdentifiers.DefaultAspireContainerNetwork
});
```

(Note, the APIs for this all existed in 13.1, they just didn't behave as you'd expect them to)

References:
- https://github.com/dotnet/aspire/issues/7153
- https://github.com/dotnet/aspire/pull/14278