Support numeric claims in JOSE DataPower library

The IBM DataPower JOSE library does not support numeric values for claims - it should according to the spec.

We have a production implementation of the Open Banking specification. As part of this we implement the Message Signing specification which uses a JSON Web Token (this must be a JSON number representing the number of seconds from 1970-01-01T0:0:0Z as measured in GMT until the date/time. )

There are various claims in the JWT protected header. One of these needs to be a numeric value : http://openbanking.org.uk/iat

https://openbanking.atlassian.net/wiki/spaces/DZ/pages/641992418/Read+Write+Data+API+Specification+-+v3.0#Read/WriteDataAPISpecification-v3.0-MessageSigning

If a numeric value is supplied - the JOSE library throws an error when parsing it

var jwsObject = jose.parse(jwsRequestHeader)

Error: mpgw (webapi): Invalid type 'number (1554393946)' detected on method invocation. Method name: setProtected; Parameter index: 1; Expected type: string

This is related to an earlier RFE (id: 129394) we raised which had a similar issue with Boolean values not being supported (for the b64 claim):

https://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=129394

A patch was released to us early - we ask the same for this (with increased urgency as this is now in production)