fix(test): add HTTPTransport stubs to prevent hanging in TestAzureGithubOIDCCredentials

EnsureResolved now calls resolveHostMetadata, which makes a real network
request when no HTTPTransport is set. Four test cases with a Host but no
transport were hanging indefinitely. Add an empty MappingTransport to each
so the host-metadata request gets a fast "missing stub" error and falls
back gracefully.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Alex Ausch <alex@ausch.name>

Author: aausch

NEXT_CHANGELOG.md

@@ -21,6 +21,7 @@
 ### Internal Changes
 
  * Normalize internal token sources on `auth.TokenSource` for proper context propagation ([#1577](https://github.com/databricks/databricks-sdk-go/pull/1577)).
+ * Fix `TestAzureGithubOIDCCredentials` hang caused by missing `HTTPTransport` stub: `EnsureResolved` now calls `resolveHostMetadata`, which makes a real network request when no transport is set ([#1550](https://github.com/databricks/databricks-sdk-go/pull/1550)).
  * Bump golang.org/x/crypto from 0.21.0 to 0.45.0 in /examples/slog ([#1566](https://github.com/databricks/databricks-sdk-go/pull/1566)).
  * Bump golang.org/x/net from 0.23.0 to 0.33.0 in /examples/slog ([#1127](https://github.com/databricks/databricks-sdk-go/pull/1127)).
  * Bump golang.org/x/oauth2 from 0.20.0 to 0.27.0 ([#1563](https://github.com/databricks/databricks-sdk-go/pull/1563)).

config/auth_azure_github_oidc_test.go

@@ -49,6 +49,7 @@ func TestAzureGithubOIDCCredentials(t *testing.T) {
 				AzureTenantID:              "test-tenant-id",
 				ActionsIDTokenRequestURL:   "http://endpoint.com/test?version=1",
 				ActionsIDTokenRequestToken: "token-1337",
+				HTTPTransport:              fixtures.MappingTransport{},
 			},
 			wantErrPrefix: errPrefix("github-oidc-azure auth: not configured"),
 		},
@@ -79,6 +80,7 @@ func TestAzureGithubOIDCCredentials(t *testing.T) {
 				AzureClientID:              "test-client-id",
 				ActionsIDTokenRequestURL:   "http://endpoint.com/test?version=1",
 				ActionsIDTokenRequestToken: "token-1337",
+				HTTPTransport:              fixtures.MappingTransport{},
 			},
 			wantErrPrefix: errPrefix("github-oidc-azure auth: not configured"),
 		},
@@ -94,6 +96,7 @@ func TestAzureGithubOIDCCredentials(t *testing.T) {
 				AzureTenantID:            "test-tenant-id",
 				Host:                     "http://host.com/test",
 				ActionsIDTokenRequestURL: "http://endpoint.com/test?version=1",
+				HTTPTransport:            fixtures.MappingTransport{},
 			},
 			wantErrPrefix: errPrefix("github-oidc-azure auth: not configured"),
 		},
@@ -109,6 +112,7 @@ func TestAzureGithubOIDCCredentials(t *testing.T) {
 				AzureTenantID:              "test-tenant-id",
 				Host:                       "http://host.com/test",
 				ActionsIDTokenRequestToken: "token-1337",
+				HTTPTransport:              fixtures.MappingTransport{},
 			},
 			wantErrPrefix: errPrefix("github-oidc-azure auth: not configured"),
 		},