TODO

> May need to have all the xmlns files local (& update sample test/responses to use them).
> Add in a filter or pre-process to allow snake_case for input array data rather than camelCaseAsPerRM.
> Add code coverage analysis.
> Add failure tests for validators and filters.
> Move more fully to Valitron validators.
> Better handling for multi-values in the interpreters - currently only handles them with nesting.
> > Could do with separating it out as the handling is different in Builder and Interpreter and currently requires bypass to avoid conflict.
> createShipment needs the multi-option values setting up.
> Automatic error minimising way to check request conversion schema completeness - parse WSDL for all possible values?
> May not need the success flag on responses - any failure should have an error response.
> Catch SOAP error objects and pass them back in the same object format? or throw a standard (interface unrelated) error the interpreter can parse.
> > Layout of items input could be tidied a lot - e.g. ~/items/ as root array with number of separate, weight doesn't need value subkey.
> SOAP response verification/security.
> printManifest request requires at least one value.
> SOAP client can be intitialised with 'features' => SOAP_SINGLE_ELEMENT_ARRAYS -- may save some work.