Short-circuit API rate limiter for unauthenticated users (#607)

### Major
- Short-circuit API rate limiter for unauthenticated user
  Calls by unauthenticated users were failing at API rate limiter as it
  failed to access user info object. This is a bug.
  
  API rate limiter should short-circuit for unauthenicated users so a
  proper Forbidden response can be returned by API
  
  Add regression test to verify that unauthenticated users get 403
  response when calling the /chat API endpoint
  
### Minor
- Remove trailing slash to normalize khoj url in obsidian plugin settings
- Move used /api/config API controllers into separate module
- Delete unused /api/beta API endpoint
- Fix error message rendering in khoj.el, khoj obsidian chat
- Handle deprecation warnings for subscribe renew date, langchain, pydantic & logger.warn

tests/test_client.py

@@ -1,4 +1,5 @@
 # Standard Modules
+import os
 from io import BytesIO
 from urllib.parse import quote
 
@@ -482,6 +483,21 @@ def test_user_no_data_returns_empty(client, sample_org_data, api_user3: KhojApiU
     assert response.json() == []
 
 
+@pytest.mark.skipif(os.getenv("OPENAI_API_KEY") is None, reason="requires OPENAI_API_KEY")
+@pytest.mark.django_db(transaction=True)
+def test_chat_with_unauthenticated_user(chat_client_with_auth, api_user2: KhojApiUser):
+    # Arrange
+    headers = {"Authorization": f"Bearer {api_user2.token}"}
+
+    # Act
+    auth_response = chat_client_with_auth.get(f'/api/chat?q="Hello!"&stream=true', headers=headers)
+    no_auth_response = chat_client_with_auth.get(f'/api/chat?q="Hello!"&stream=true')
+
+    # Assert
+    assert auth_response.status_code == 200
+    assert no_auth_response.status_code == 403
+
+
 def get_sample_files_data():
     return [
         ("files", ("path/to/filename.org", "* practicing piano", "text/org")),