For now we are not using the right code (as defined in the guidelines) for error in the OAS examples.

For 400 should be INVALID_ARGUMENT instead of INVALID_INPUT
for 401 ... UNAUTHENTICATED and not UNAUTHORIZED
same mismatch for 403, 500 & 503

This indirectly link to #15

@jlurien as it is only example change I can probably fix this now without changing version no?