Library doesn't implement error.id

[aljones15]

Note: this is a bit speculative as VC-API 0.3 does not seem to have consensus on what the error objects should look like, but this is the current data structure:

id [string]
message [string]
details [object]

We return:

    name: 'ValidationError',
    message: "A validation error occured in the 'Initiate Exchange Request' validator.",
    details: { errors: [Array], httpStatusCode: 400 },
    cause: null,
    stack: "ValidationError: ...',
    type: 'ValidationError'

So when the error formats for the VC-API are formalized we will need to update this library and probably vc-delivery too.

[dlongley]

I'm not sure we want the errors to look like what's in the spec. We should decide if that's a good idea or if we should adopt a different format before making implementation changes.