Investigate intermittent issues with OAI when downloading images

[monsieurBoutte]

OpenAI likely has some pretty strict criteria around the availability of images being sent to their server. Some got'chas to consider as we look further into this:

• Converting to base64 may not always be a safe option unless we always downsample to a much lower resolution but this in turn could hinder the results we're expecting for a moderation call
• If we use Mux's thumbnail API, there's a just in time tax to be paid which means introduced latency. We can potentially combat this by doing a simple fetch on that url before forwarding it along to OAI.