Find a way to get credentials with `validFrom` and/or `validTo` set by someone/something else.

[BigBlueHat]

This test needs writing:

vc-data-model-2.0-test-suite/tests/4-9-validity-period.js

Lines 116 to 126 in a9f2160

	// 4.8.1 Representing Time https://w3c.github.io/vc-data-model/#representing-time
	it('Time values that are incorrectly serialized without an offset ' +
	'MUST be interpreted as UTC.', async function() {
	this.test.link = `https://w3c.github.io/vc-data-model/#validity-period:~:text=Time%20values%20that%20are%20incorrectly%20serialized%20without%20an%20offset%20MUST%20be%20interpreted%20as%20UTC.`;
	// TODO: add test using regular expression from spec.
	// https://w3c.github.io/vc-data-model/#example-regular-expression-to-detect-a-valid-xml-schema-1-1-part-2-datetimestamp
	// eslint-disable-next-line max-len, no-unused-vars
	const regexp = /-?([1-9][0-9]{3,}|0[0-9]{3})-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])T(([01][0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9](\.[0-9]+)?|(24:00:00(\.0+)?))(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))/;
	this.test.cell.skipMessage = 'TBD';
	this.skip();
	});

It's blocked by the fact that we send fixtures out to either (or both) issue or verify...so the test suite is only currently handling whether the receiving end can receive and process valid inputs (or chokes on invalid ones). It doesn't currently test received data it hasn't previously known about. Which makes this test particularly problematic.