add comments to explain non-intuitive logic in test

Author: XcrigX

src/test/java/ca/uhn/fhir/jpa/starter/CdsHooksServletIT.java

@@ -88,6 +88,13 @@ void beforeEach() {
 
 	private Boolean hasCdsServices() throws IOException {
 		var response = callCdsServicesDiscovery();
+
+		// NOTE: this is looking for a repsonse that indicates there are CDS services availalble.
+		// And empty response looks like: {"services": []}
+		// Looking at the actual response string consumes the InputStream which has side-effects, making it tricky to compare the actual contents.
+		// Hence the test just looks at the length to make this determination.
+		// The actual response has newlines in it which vary in size on some systems, but a value of 25 seems to work across linux/mac/windows
+		// to ensure the repsonse actually contains CDS services in it
 		return response.getEntity().getContentLength() > 25 || response.getEntity().isChunked();
 	}