bug: Use Indexify Client with downloader.py and task reported.py in Extractor Agent

[Default2882]

Context -

While working on #1007 I realised that, downloader.py and task_reporter.py use the basic httpx client instead of the IndexifyClient wrapper for httpx.

Why is this bad -

IndexifyClient has an optional parameter to take in the api_key, as per the current implementation the downloader and task_reporter will stop working if the server expects an api_key, and this needs to be fixed.

Fix -

Simply use IndexifyClient instead of httpx client, reference can be taken from this PR #1046

[Default2882]

As per discussion on discord -
"We trust the executor to not need api keys to talk to the server. The client is meant to be used by user code which is untrusted. The open source server doesn’t have any security mechanisms built in. We expect folks building a platform with indexify to build their authentication mechanisms on top."

[Default2882]

Closing