Many of the configuration keys in the doc/2-configuring.md file seem to be incorrect. When inspecting the code, `.toLowerCase` is called on several of them. In particular, "sampleSize" or "samplesize". It looks like `ReadConfigSpec.scala` uses the working configuration keys. This also affects partitioning options i.e. "partitionKey".

This also affects https://docs.mongodb.com/spark-connector/current/configuration/