Verify 500 responses hit source twice via call counter

Adds tables.CacheOfHttp.serverErrorCalls counter (matching the
CacheOfResource.sourceGetsPerformed pattern) so the non-cacheable 500
test can assert the source was invoked on both requests rather than
relying on server-timing headers.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: kriszyp

unitTests/apiTests/basicREST-test.mjs

@@ -457,6 +457,7 @@ describe('test REST calls', () => {
 			assert(!response2.headers['server-timing'].includes('miss'));
 		});
 		it('does not cache a non-cacheable 500 response', async () => {
+			const callsBefore = tables.CacheOfHttp.serverErrorCalls;
 			const response = await axios.get('http://localhost:9926/CacheOfHttp/server-error', {
 				validateStatus: () => true,
 			});
@@ -466,6 +467,7 @@ describe('test REST calls', () => {
 				validateStatus: () => true,
 			});
 			assert.equal(response2.status, 500);
+			assert.equal(tables.CacheOfHttp.serverErrorCalls, callsBefore + 2);
 		});
 		it('does not store status in cached record for 200 responses', async () => {
 			// The CacheOfHttp 'created-response' source returns a 200 with a custom header

unitTests/testApp/resources.js

@@ -169,6 +169,7 @@ tables.CacheOfResource.sourcedFrom({
 });
 
 // test transparent HTTP caching straight through
+tables.CacheOfHttp.serverErrorCalls = 0;
 tables.CacheOfHttp.sourcedFrom({
 	async get(target) {
 		switch (target) {
@@ -197,6 +198,7 @@ tables.CacheOfHttp.sourcedFrom({
 			case 'not-found':
 				return new Response('Not Found', { status: 404 });
 			case 'server-error':
+				tables.CacheOfHttp.serverErrorCalls++;
 				return new Response('Internal Server Error', { status: 500 });
 		}
 	},