feat: add invocation fixtures

[alanshaw]

This is a collection of 20 dag-json encoded fixtures testing various aspects of invocations.

Specifically they are vectors for the following cases:

• A valid invocation with no proofs, the subject is the issuer so no proof is necessary
• A valid invocation with a single proof that has no expiry
• A valid invocation with a single proof that has no expiry and is active (a not before timestamp in the past)
• A valid invocation with a proof chain more than one delegation long
• A valid invocation with a proof chain more than one delegation long where one or more proofs have an not before time in the past
• A valid invocation with a proof chain with a powerline delegation (null value for subject)
• A valid invocation with a policy that matches the invocation arguments
• An invalid invocation because it has no proofs
• An invalid invocation because a proof is not provided or resolvable externally
• An invalid invocation because a proof is expired
• An invalid invocation because a proof has a not before time in the future
• An invalid invocation because the audience of a delegation in the proof chain is not the issuer of the next delegation
• An invalid invocation because the audience of the delegation is not the issuer of the invocation
• An invalid invocation because the subject is not the same for every delegation in the proof chain
• An invalid invocation because the subject of the invocation is not the same as the subject of the delegation
• An invalid invocation because the invocation is expired
• An invalid invocation because the signature of a proof is not verifiable
• An invalid invocation because the signature of the invocation is not verifiable
• An invalid invocation because the root delegation has a null subject
• An invalid invocation because the invocation violates a policy set in an delegation

The vectors are built by the script here and I have opened a corresponding PR to go-ucan that exercises these vectors.

[cla-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have the users @alanshaw on file. In order for us to review and merge your code, please contact the project maintainers to get yourself added.

[cla-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have the users @alanshaw on file. In order for us to review and merge your code, please contact the project maintainers to get yourself added.