Add comprehensive test suite for image processing and related services

- Implement tests for database generator to ensure proper session handling.
- Create tests for EXIF extraction and conversion functions.
- Add tests for image-related endpoints, ensuring proper data retrieval and isolation between clients.
- Develop tests for OCR functionality, including language detection and text extraction.
- Introduce tests for the image processing pipeline, covering success and failure scenarios.
- Validate rate limiting functionality and ensure independent counters for different clients.
- Implement scraper tests to verify HTML content fetching and error handling.
- Add unit tests for various services, including storage and filename generation.
- Establish worker entry point for ARQ to handle background image processing tasks.

tests/test_middleware_extended.py

@@ -0,0 +1,34 @@
+import pytest
+from unittest.mock import MagicMock
+from app.middleware import (
+    _get_client_id_from_request, get_upload_rate_limit, 
+    get_ai_rate_limit, upload_rate_limit_key, ai_rate_limit_key
+)
+
+def test_get_client_id_from_request_with_id():
+    request = MagicMock()
+    request.state.client_id = "test-client"
+    assert _get_client_id_from_request(request) == "test-client"
+
+def test_get_client_id_from_request_fallback():
+    request = MagicMock()
+    del request.state.client_id # Ensure it's not there
+    request.client.host = "1.2.3.4"
+    request.headers = {}
+    
+    # slowapi's get_remote_address uses request.client.host or headers
+    with patch("app.middleware.get_remote_address", return_value="1.2.3.4"):
+        assert _get_client_id_from_request(request) == "1.2.3.4"
+
+from unittest.mock import patch
+
+def test_rate_limit_helpers():
+    assert "hour" in get_upload_rate_limit("free")
+    assert "hour" in get_ai_rate_limit("premium")
+    assert get_upload_rate_limit("invalid") == get_upload_rate_limit("free")
+
+def test_rate_limit_keys():
+    request = MagicMock()
+    request.state.client_id = "abc"
+    assert upload_rate_limit_key(request) == "abc"
+    assert ai_rate_limit_key(request) == "abc"