Explore "exhausted input" errors

[chuwy]

I've seen this several times in test environments, but never paid any attention. Recently I saw it for the first time in production pipeline and now we have OSS user mentioning it: https://discourse.snowplowanalytics.com/t/bad-enrichment-invalid-json-exhausted-input/4253

This message comes from circe when it cannot parse a string into valid Json, usually because server responded with empty or truncated string.

However, I'm not sure that this is actually circe's problem - very likey the culprit is the HTTP cilent we use (scalaj) or actual Iglu Server, although I've never seen this with json4s (pre-0.6.0 Iglu clilent)