Support dynamically creating issuance sessions on the PAR request handler

[hacdias]

Follow-up issue for #2474.

We should add support for dynamically creating issuance sessions on the PAR request handler. This can be probably done using a callback. However, we need to figure out what type of information we need to send to the PAR endpoint in order to make it possible, and within the limits of the specifications.

credo-ts/packages/openid4vc/src/openid4vc-issuer/router/pushedAuthorizationRequestEndpoint.ts

Lines 257 to 264 in cd6c836

	// TODO: we could allow dynamic issuance sessions here. Maybe based on a callback?
	// Not sure how to decide which credentials are allowed to be requested dynamically
	if (!parseResult.authorizationRequest.issuer_state) {
	throw new Oauth2ServerErrorResponseError({
	error: Oauth2ErrorCodes.InvalidRequest,
	error_description: `Missing required 'issuer_state' parameter. Only requests initiated by a credential offer are supported for pushed authorization requests.`,
	})
	}