[release/9.4] External Services with URL Parameter fails to generate manifests (dotnet#10806)

* External Services with URL Parameter fails to generate manifests

Need to check for publish mode before calling GetValueAsync on the URL parameter

Fix dotnet#10789

* Add test

* Fix test to not use Verify

---------

Co-authored-by: Eric Erhardt <[email protected]>

Author: 2 people

tests/Aspire.Hosting.Tests/ExternalServiceTests.cs

@@ -446,7 +446,20 @@ public async Task ExternalServiceWithParameterPublishManifest()
 
         var manifest = await ManifestUtils.GetManifest(project.Resource);
 
-        await Verify(manifest.ToString(), extension: "json");
+        Assert.Equal(
+            """
+            {
+              "type": "project.v0",
+              "path": "testproject",
+              "env": {
+                "OTEL_DOTNET_EXPERIMENTAL_OTLP_EMIT_EXCEPTION_LOG_ATTRIBUTES": "true",
+                "OTEL_DOTNET_EXPERIMENTAL_OTLP_EMIT_EVENT_LOG_ATTRIBUTES": "true",
+                "OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY": "in_memory",
+                "services__external__default__0": "{external-url.value}",
+                "EXTERNAL_SERVICE": "{external-url.value}"
+              }
+            }
+            """, manifest.ToString());
     }
 
     private sealed class TestProject : IProjectMetadata