attachInvocationProof takes both a key and a signer

[aljones15]

did-veres-one/lib/attachProof.js

Lines 106 to 131 in fbd9fc8

	/**
	* Adds a zcap-style invocation proof to an operation.
	*
	* @param {object} operation - WebLedger operation.
	*
	* @param {object} options - Options hashmap.
	* @param {string} capability - Capability (DID) url.
	* @param {string} capabilityAction - 'create' / 'update'.
	*
	* Either a key pair instance or a signer object (from a KMS) is required:
	* @param {LDKeyPair} [options.key] - A capabilityInvocation
	* public/private key pair instance.
	* @param {{sign: Function, id: string}} [options.signer] - A signer-type object
	* such as that provided by a KMS.
	*
	* @returns {Promise<object>}
	*/
	async function attachInvocationProof(operation, {
	capability, capabilityAction, key, signer
	} = {}) {
	return jsigs.sign(operation, {
	documentLoader,
	suite: new Ed25519Signature2020({key, signer}),
	purpose: new CapabilityInvocation({capability, capabilityAction})
	});
	}

Questions:

1. Why do we need both a signer and a key?
2. Can we just pass in one of them?

Answer:

1. I believe we accommodate passing in either a key or signer. We might want to make sure you're only passing in one with a warning.