Check if the given request needs conversion and perform those conversions.
This method is supposed to create a mutable request and to modify and returns that one. However in case of
error it won't return the modified request, but it will handle directly the errors in the response.
request - the request that might contain parameter needing conversion
response - the response used to redirect or do changes in case of conversion error
a mutable request with the converted parameters, or an empty optional in case of error
IOException - in case of problem to write an answer in the response