handle kinesis large values

[rotemseekingalpha]

add producer_max_value_size
remove largest value (> producer_max_value_size) recursively from RowMap.data

[osheroff]

intersting approach. I wouldn't want this on by default, but I could see it as an option; cut out large blobs but get the important bits in by default.

For me to merge this PR I think:

• there'd need to be tests. This probably means extracting the code into a module somewhere.
• there'd need to be configuration to turn it on
• it should work for kafka too.