Feature Request: Add msg authz grant and revoke

[puneet2019]

till #129 is ready and can allow encoding of arbitrary types, we can have authz grant and revoke, so multisig participants can use UI for certain msg types by giving authz to any address ( for a day or so) and optionally revoking it if the address is corrupted.

[puneet2019]

oh its a part of #99 !
cosmos-sdk chains 47.x + support authz via ledgers (most of them are)

[abefernan]

It looks like CosmJS does not yet support signing those with ledgers https://github.com/cosmos/cosmjs/blob/main/packages/stargate/src/modules/authz/aminomessages.ts

[abefernan]

Not yet solved, but added to #99