fix: add supportsGet guard to getResource

Short-circuit getResource for resource types that don't support GET
(e.g. ProductGroup, ProductApi, GatewayApi) before making a network
call. This centralizes the guard and makes pollAsyncOperation safe
for all resource types.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Peter Hauge

src/clients/apim-client.ts

@@ -302,6 +302,14 @@ export class ApimClient implements IApimClient {
     context: ApimServiceContext,
     descriptor: ResourceDescriptor
   ): Promise<Record<string, unknown> | undefined> {
+    // Some association resources (ProductGroup, ProductApi, GatewayApi) only
+    // support PUT/DELETE. Short-circuit before making a network call.
+    const metadata = RESOURCE_TYPE_METADATA[descriptor.type];
+    if (!metadata.supportsGet) {
+      logger.debug(`Resource type ${descriptor.type} does not support GET, returning undefined`);
+      return undefined;
+    }
+
     const url = buildArmUri(context, descriptor);
     // Azure APIM returns HTTP 500 (not 404) when an API or product has no wiki.
     // Suppress retries for wiki types so the extractor silently skips them.