Add comments in the Anthropic route for the header invariant key hack.

proxy/routes/anthropic.py

@@ -57,6 +57,16 @@ async def anthropic_v1_messages_proxy(
     headers["accept-encoding"] = "identity"
 
     # In case the user wants to push to Explorer, the request must contain the Invariant API Key
+    # The invariant-authorization header contains the Invariant API Key
+    # "invariant-authorization": "Bearer <Invariant API Key>"
+    # The x-api-key header contains the Anthropic API Key
+    # "x-api-key": "<Anthropic API Key>"
+    #
+    # For some clients, it is not possible to pass a custom header
+    # In such cases, the Invariant API Key is passed as part of the
+    # x-api-key header with the Anthropic API key.
+    # The header in that case becomes:
+    # "x-api-key": "<Anthropic API Key>|invariant-auth: <Invariant API Key>"
     invariant_authorization = None
     if dataset_name:
         if request.headers.get(
@@ -73,7 +83,7 @@ async def anthropic_v1_messages_proxy(
             header_value = request.headers.get(ANTHROPIC_AUTHORIZATION_HEADER)
             api_keys = header_value.split("|invariant-auth: ")
             invariant_authorization = f"Bearer {api_keys[1].strip()}"
-            # Update the authorization header to pass the OpenAI API Key to the OpenAI API
+            # Update the authorization header to pass the Anthropic API Key
             headers[ANTHROPIC_AUTHORIZATION_HEADER] = f"{api_keys[0].strip()}"
 
     request_body = await request.body()