fix(clerk): add alternative decoder

[jtoar]

Working fix for #8641. This is a work in progress; I haven't tested it yet, I just want to get the conversation started. @asher-eastham, @o0charlie0o, would love your input here. @asher-eastham I think what I'm proposing here is along the lines of what I suggested to you, but curious to know how much your implementation ended up differing?

I know the existing authDecoder needs to go, but removing that would be breaking. What if we mark it as deprecated, add a new authDecoder (right now named jwtAuthDecoder, but open to suggestions), configure the yarn rw setup auth clerk command to use that decoder instead, and in the release notes, I'll recommend everyone use Clerk use the new decoder?

• docs on how to customize the JWT

[jtoar]

It seems I have some work to do with the template getCurrentUser function. It passes the decoded token to parseJWT which doesn't seem to do the right thing anymore. Let me double check what it does with the existing decoded token, but with my changes, I'm getting back an object like this: This is what parseJWT returns in stable, so this behavior is expected.

{ appMetadata: {}, roles: [] }

It still feels like the template getCurrentUser needs to be updated. @o0charlie0o and @asher-eastham do you use parseJWT at all in your getCurrentUser function? I'm going to ask the team what the intention behind it was, it doesn't seem that necessary to me for Clerk.

[o0charlie0o]

@jtoar We do not use parseJWT at all.