T-6088 Send correct Content-Encoding HTTP header

[PetrHeinz]

Previously, Content-Encoding gzip was sent, but deflate was used to compress the data

Fixes #34

[gyfis]

@PetrHeinz do you want to go the other way around, e.g. gzip the actual data instead? That should give better default compression

[PetrHeinz]

@gyfis Tried to do it in #38 , but doesn't seem to be working when run against real ingestion. I'd merge it with the deflate compression. WDYT?

[adikus]

@gyfis Deflate and gzip are the same compression, they only differ in headers from what I understand, so should be no difference in compression levels.

[gyfis]

Ah, my bad then, sorry! Got confused as well