ui: handle incoming base64 strings from grpc-web

[grottohub]

fixes #1923

Quick synopsis of the issue: data being received for the fields waypointHcl and privateKeyPem is being transmitted as base64 encoded strings, which was unaccounted for when rendering that data in the UI, leading it to display the base64 encoded strings instead of the readable data.

The approach for this solution allows the data to continue "living" as base64, and is simply decoded when rendered in the UI (via computed properties decodedWaypointHcl and decodedPrivateKey). A caveat here is the on "input" event listeners. If a user doesn't trigger that event (i.e. they don't change the value), there's no need to re-encode that field back to base64 to be sent to the server. This is why I chose to let the data stay as a base64 string - encoding will happen on input (in the actions setWaypointHcl and setSshAuth), thus removing the need to encode the data on form submission.

[gregone]

@grahamhub Thanks for investigating the bug and for taking the time to dive into this with @jgwhite ! The approach is good, and after trying it out, everything works as expected. 🎉

I just had to push a changelog entry in 320d29c to make the checks pass on our side.

Thanks for contributing 💯 !

[grottohub]

thanks for the quick review @gregone - glad to have contributed to something I've been using extensively!