support keeping the original serde field names

[eliad-wiz]

SCREAMING_SNAKE_CASE might not be the expected format, so allow keeping the original serde field names

What did you implement:

a new keep_names() functionthat can be used in order to keep the original serde field names (api is similar to the prefixed() function)

Closes: #61

How did you verify your change:

a new unit-test was added

What (if anything) would need to be called out in the CHANGELOG for the next release: