Changes to Search flights

the response property advice became nullable for the status 200

the response property advice became optional for the status 200

the advice response's property default value was removed for the status 200

removed subschema #1 subschema #2 subschema #3 from the trip request property oneOf list

added subschema #1 subschema #2 subschema #3 to the trip request property oneOf list

added the non-success response with the status 422

added the required property advice to the response with the 200 status