Clear Sonar S5332 http-scheme hotspot on rest API test

Lift the ``http`` scheme into a named constant with a NOSONAR justification
so the static analyzer sees intent ("localhost-only ephemeral test server;
TLS is out of scope") rather than a bare ``http://`` URL literal. The test
still hits the same local server in the same way.

Author: JE-Chen

test/unit_test/headless/test_rest_server.py

@@ -16,9 +16,12 @@ def rest_server():
     server.stop(timeout=1.0)
 
 
+_TEST_SCHEME = "http"  # NOSONAR: S5332  # reason: localhost-only ephemeral test server; TLS is out of scope here
+
+
 def _request(server, path, method="GET", body=None):
     host, port = server.address
-    url = f"http://{host}:{port}{path}"
+    url = f"{_TEST_SCHEME}://{host}:{port}{path}"
     data = None
     headers = {}
     if body is not None: