cli: auth command should use admin RPC

[Wondertan]

          [discussion]

This should become a call on Admin.AuthNew. Likely in a separate PR

Originally posted by @Wondertan in #2762 (comment)

[vgonkivs]

After some work on this issue, I've realized that we should leave auth cmd as it is, bc in order to create a client, we already have to have an auth token. I've tested several use cases(run a LN and create a token for the LN - it works, run a LN - create a token for the FN - it also works, but that is incorrect). We also have a set-permission cmd that does completely the same as your suggested version of AuthCmd(). So, we discussed it with @renaynay internally and decided to leave this particular cmd as it is.

[ramin]

it sounds like the decision has been made to NOT proceed with this? @vgonkivs can you confirm and close

[Wondertan]

bc in order to create a client, we already have to have an auth token.

That's totally fine as we always have the main key generated in KeyStore, so we always have a key to use and that's by design.

I don't think we should close this yet.