Extend options to support passthrough

[emmjohnson]

Description of problem

Today, if a workload does not match any of the options, we explode. We are suggesting that it is possible that a workload purposely does not want to match any of the options and would instead like the ability to move on to the next step.

Proposed solution

https://gist.github.com/squeedee/ed833b036ecc8f983d5aaf5801cc5fa8

[emmjohnson]

Do we have any thoughts what the shape of status.resource[x] should be for the "skipped" resource?

Possibly:

    - name: source-tester
      inputs:
        - name: source-provider
       outputs:
        - name: url
          preview: |
           ...
        - name: revision
          preview: |
            ...

Leaving out stampedRef, templateRef, and conditions