added requiring call sites to set own content-type for anything other than json(aioweb doesn't set content-type properly)

src/monitor_utils/sessions.py

@@ -84,10 +84,11 @@ async def send_request(
         url: Request URL.
         method: HTTP method.
         params: Query parameters.
-        json_data: JSON body. A dict here is sent as a JSON body.
-        data: Alternative body. Note aioweb routes any dict or list to a JSON
-            body, so true form-encoding requires a pre-encoded string; a form
-            dict passed here is sent as JSON.
+        json_data: JSON body. A dict here is sent as JSON with the
+            application/json content-type set by aioweb.
+        data: Raw request body, passed through unchanged (e.g. a url-encoded
+            form string). The caller owns the matching content-type via headers.
+            A dict is JSON-encoded by aioweb, so use json_data for JSON bodies.
         headers: Per-request headers merged over the session defaults.
 
     Returns: