Serialization of too many records can result in a 502 timeout

[bctcvai]

When fetching millions of records in a single rest request, its possible the request ends up resulting in a 502 timeout. It would be more elegant and proper to return a 400 error. Presumably a maximum record size would be specified.

Some experimentation should be done to determine what this size should be by benchmarking request times at 50K,100K,250K,500K, and 1M. On /rest/Medias considerations include the time it takes to generate a presigned URL, per record, in response. It seems like a limit around 100K or 250K would not impact existing usages, but it would be informative to know what that means in wall clock time.

If the limit was 50K or less, considerations to reworking the annotator UI would need to be done. Videos with dense tracks often have tens of thousands of detentions and currently fetched in a single call.