Factorize getting the request parameters length and offset
Factorize getting the request parameters `length` and `offset` from the service routes (/rows, /search and /filter) to `libapi`.
Additionally, align their error messages.
Factorize getting the request parameters length and offset: Factorize getting the request parameters `length` and `offset` from the service routes (/rows, /search and /filter) to `libapi`.
Additionally, align their error messages.