Add support for fetching thumbnails separately

[dermotduffy]

• An upcoming integration change will require uses of the BrowseMedia API to fetch thumbnails separately rather than using embedded base64 encoded thumbnails. This will result in a slightly worse card experience (thumbnails may take a very short time to load vs the appearance of being instantaneous) but allows encoded thumbnails to be removed from the database on the Frigate side.

Related PR: blakeblackshear/frigate-hass-integration#322

[uvjustin]

This seems like a good solution as it avoids some of the pitfalls you mentioned with the other approach. One thing to think about is the interaction with the service worker/cache. I ended up putting "static" in the new ThumbnailsProxyView endpoint name which means the assets should get cached by the service worker. I'm not sure, but that might also make the auth unnecessary after the first load.

[dermotduffy]

OK -- lets go with this one for now then so we can unblock your integration PR.

I'm not sure, but that might also make the auth unnecessary after the first load.

Yeah, but I'm not sure how to take advantage of that possibility easily without implementing an internal "has-loaded" cache and hoping the browser does the right thing...