Validate Defaults

[raphaelhetzel]

The defaults are currently not validated,
what could lead to errors especially in the case of the sort options or other parsers with more complex output.
This could be verified but as the defaults are defined in code and this would also slow down the handler,
i'm not sure how whether this should be done. A different solution would be to provide a way to easily spec this (Shared Examples?).

[andreaseger]

hmm maybe we can verify the defaults once during definition. That way we have both benefits no overhead for the request parsing and validated default options