Add to Pinniped.dev: FederationDomain transformation playground

[benjaminapetersen]

It would be interesting to host on the docs for transformations a "playground" that:

• Takes a JWT input
• Takes a set of transformations
• gives an output

We have the "examples" as mini unit-tests for this feature. Super cool. Currently this works on just the string usernames & groups. It would be interesting to have something that would input the full JWT and see the output.

Something kind of like CEL Playground:

• https://playcel.undistro.io/

Looks like the library powering that is here:

• https://github.com/undistro/cel-playground

And that is is hosted in browser, no server-side component necessary.

Carvel has some interactive bits on their website, can be handy for tinkering without needing a full environment running. JWT.io also has some interactive helpful tools:

• https://jwt.io/
• https://carvel.dev/ytt/ (scroll down)