Work around need for large plugins

[SPlanzer]

The maximum payload to API gateway is 10MB and maximum payload for Lambda is 6MB, which cannot be increased.

https://docs.aws.amazon.com/apigateway/latest/developerguide/limits.html
https://docs.aws.amazon.com/lambda/latest/dg/gettingstarted-limits.html

These limits were not understood at the time of development but did affected one plugin during migration (see #126). All other LINZ plugins were of a smaller enough size they were not affected by payload size limits.

There are a number of documented workarounds for this, including uploading directly to s3 via signed urls (https://sookocheff.com/post/api/uploading-large-payloads-through-api-gateway/)