Wait for OPA to load rules in tests startup (#5483)

OPA can take some time to load rules, but our tests don't wait for OPA,
and start right after the server is loaded.
Sometimes it works, but in other times the tests may fail because OPA is
still loading the rules.
This PR allows to wait for OPA during the test suite startup.

tests/python/shared/fixtures/init.py

@@ -2,6 +2,7 @@
 #
 # SPDX-License-Identifier: MIT
 
+import logging
 import re
 from http import HTTPStatus
 from pathlib import Path
@@ -11,7 +12,9 @@
 import pytest
 import requests
 
-from shared.utils.config import ASSETS_DIR, get_api_url
+from shared.utils.config import ASSETS_DIR, get_server_url
+
+logger = logging.getLogger(__name__)
 
 CVAT_ROOT_DIR = next(dir.parent for dir in Path(__file__).parents if dir.name == "tests")
 CVAT_DB_DIR = ASSETS_DIR / "cvat_db"
@@ -185,12 +188,24 @@ def delete_compose_files():
         filename.unlink(missing_ok=True)
 
 
-def wait_for_server():
-    for _ in range(30):
-        response = requests.get(get_api_url("users/self"))
-        if response.status_code == HTTPStatus.UNAUTHORIZED:
-            break
-        sleep(5)
+def wait_for_services():
+    for i in range(300):
+        logger.debug(f"waiting for the server to load ... ({i})")
+        response = requests.get(get_server_url("api/server/health/", format="json"))
+        if response.status_code == HTTPStatus.OK:
+            logger.debug("the server has finished loading!")
+            return
+        else:
+            try:
+                statuses = response.json()
+                logger.debug(f"server status: \n{statuses}")
+            except Exception as e:
+                logger.debug(f"an error occurred during the server status checking: {e}")
+        sleep(1)
+
+    raise Exception(
+        "Failed to reach the server during the specified period. Please check the configuration."
+    )
 
 
 def docker_restore_data_volumes():
@@ -286,7 +301,7 @@ def pytest_sessionstart(session):
             pytest.exit("All testing containers are stopped", returncode=0)
 
         start_services(rebuild)
-        wait_for_server()
+        wait_for_services()
 
         docker_exec_cvat("python manage.py loaddata /tmp/data.json")
         docker_exec_cvat_db(
@@ -303,7 +318,7 @@ def pytest_sessionstart(session):
         kube_cp(CVAT_DB_DIR / "restore.sql", f"{db_pod_name}:/tmp/restore.sql")
         kube_cp(CVAT_DB_DIR / "data.json", f"{server_pod_name}:/tmp/data.json")
 
-        wait_for_server()
+        wait_for_services()
 
         kube_exec_cvat("python manage.py loaddata /tmp/data.json")