Add buildType for Chains format slsa/v2alpha2 (SLSAv1.0 predicate).

[chitrangpatel]

Changes

Fixes #890

This PR adds the build type for the implementation of the SLSA format v2alpha2 as per issue #797.

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Release Notes

Add buildType for Chains format slsa/v2alpha2 (SLSAv1.0 preficate).

/kind documentation

Looks something like this on locally hosted tekton website:

[tekton-robot]

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[chitrangpatel]

/assign @wlynch @chuangw6 @lcarva

[wlynch]

Is this the right build type?

I don't know if we should be pointing to /docs/ page - I'd prefer to carve out a more dedicated space e.g. https://tekton.dev/predicate/chains/run/v2alpha1

[chitrangpatel]

This url is what would appear if we simply merged this doc as is. This is what the Tekton Website would point to. I can certainly work towards making changes in the Tekton website as well such that the url is what we desire.

Let me start by trying to achieve something like this: https://tekton.dev/predicate/chains/run/v2alpha1

[chitrangpatel]

It is now "buildType": "https://tekton.dev/predicate/chains/slsa/v2"

[chuangw6]

Thank you @chitrangpatel for writing this up!

[lehors]

I don't mean to be pedantic but I used your samples as input to test a provenance validator and found a few typos in the json.
Also I should note that I don't believe it is valid for a URI to be relative as in:

"uri": "gcr.io/tekton-releases/github.com/tektoncd/pipeline/cmd/git-init",

Otherwise this looks good to me.
Thanks for working on adding support for SLSA 1.0!

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: chitrangpatel / name: Chitrang Patel (92217e3, 9868aa8)

[lehors]

Folks, I apologize for not realizing that this was blocked by my (simple) contribution not being covered by my company's CLA. I got this addressed and hope you can proceed with merging this PR.