[feature] Support ingesting compressed documents

[dejanb]

This is an another things that could help with #731

Currently format of Documents sent for ingestion is

type Document struct {
	Blob              []byte
	Type              DocumentType
	Format            FormatType
	SourceInformation SourceInformation
}

where Blob is the uncompressed data. For large files consumers will not be able to be ingested as NATS messages will be dropped (nats: slow consumer, messages dropped on connection).

As documents are highly compressible, it would be good to support ingesting them supporting popular compression algorithms. I think this feature can also have a wider usability, for example with proposed upload API (#1177) or downloading compressed files from S3 (also work in progress). In general we should allow people to send compressed files around if they want.

I'm currently working on draft PR for this.

[dejanb]

Implemented with #1222