GetQueryParamListValues obtains a list of strings from the provided queryVars, by parsing all values with key 'varKey' and splitting the values by commas, if they contain commas.

Slice is a utility function to cut a slice according to the provided offset and limit.

SliceStr is a utility function to cut a slice of *strings according to the provided offset and limit.

ValidatePositiveInt obtains the positive int value of query var defined by the provided varKey.