Add Status List Token validation for MSO MDoc

[dzarras]

The version of the walt.id MSO MDoc credentials library we are using is lacking support for Status List Tokens.
Given we cannot upgrade to the latest version, a workaround is needed for supporting Status List Token validations for MSO MDoc.

Checking https://github.com/ISOWG10/ISO-18013/blob/main/Working%20Documents/Working%20Draft%20ISO_IEC_18013-5_second-edition_CD_ballot_resolution_v3.pdf, we find the following:

Per 12.3.4 Signing method and structure for MSO:

MobileSecurityObject = {
  "version" : tstr,
  "digestAlgorithm" : tstr,
  "valueDigests" : ValueDigests,
  "deviceKeyInfo" : DeviceKeyInfo,
  "docType" : tstr,
  "validityInfo" : ValidityInfo
  ? "status": Status
  * tstr => RFU
}

Status = {
  ? "identifier_list" : IdentifierListInfo,
  ? "status_list : StatusListInfo,
  * tstr => RFU
}

Additionally per 12.3.6.5 Status list details:

The status_list element shall follow the requirements for the StatusListInfo structure as defined in the token status list specification with the addition of the optional Certificate element defined in 12.3.6.2.

This PR introduces Status List Token validation for MSO MDoc as follows:

1. Decode the payload of IssuerAuth, which is a MobileSecurityObject as a MapElement
2. Check if the above MapElement contains the key status
3. status must be a MapElement
4. Check if status contains the key status_list
5. Check if status_list is a MapElement that can be decoded as a StatusReference - the optional certificate element is ignored
6. If we have a valid StatusReference fetch the current Status and ensure it is Status.Valid

Closes #474