✨(backend) add fallback search & default ordering

Filter deleted documents from visited ones.
Set default ordering to the Find API search call (-updated_at)
BaseDocumentIndexer.search now returns a list of document ids instead of models.
Do not call the indexer in signals when SEARCH_INDEXER_CLASS is not defined
or properly configured.

Signed-off-by: Fabre Florian <ffabre@hybird.org>

src/backend/impress/settings.py

@@ -101,7 +101,7 @@ class Base(Configuration):
 
     # Search
     SEARCH_INDEXER_CLASS = values.Value(
-        default="core.services.search_indexers.FindDocumentIndexer",
+        default=None,
         environ_name="SEARCH_INDEXER_CLASS",
         environ_prefix=None,
     )
@@ -982,11 +982,6 @@ class Test(Base):
     # Tests are raising warnings because the /data/static directory does not exist
     STATIC_ROOT = None
 
-    # Setup indexer configuration to make test working on the CI.
-    SEARCH_INDEXER_SECRET = "ThisIsAKeyForTest"  # noqa
-    SEARCH_INDEXER_URL = "http://localhost:8081/api/v1.0/documents/index/"
-    SEARCH_INDEXER_QUERY_URL = "http://localhost:8081/api/v1.0/documents/search/"
-
     CELERY_TASK_ALWAYS_EAGER = values.BooleanValue(True)
 
     def __init__(self):