Support transfering a multisig from 1 chain to another

[Tbaut]

If a multisig has been created on a chain, it'd be good to create a multisig on another chain in a couple clicks, without having to re-create a multisig.
It should effectively create a Tx on the other chain.

[tomusdrw]

👍 Would love to see that. Having to create it manually is a bit cumbersome, but more importantly it is error prone.

[Tbaut]

I'll tackle this in the next weeks. The way I intent to solve this is to replicate any multisig on any system chain, on the other system chains. This is done on the indexer level, and users will not have to do anything.
E.g you create a tx with a multisig (with or without proxy it doesn't matter) on Relay. The indexer learns about this multisig for the first time.
-> the same multisig will be visible on Multix automatically on AH and Coretime

• Proxies will not be replicated since they are not cross chain
• It will be backward compatible and old multisigs will be replicated too
• if this creates some unintended behavior with too many multisigs in the dropdown, it can be mitigated with the newly added feature allowing to hide certain accounts per network: Allow hidding accounts #631

[tomusdrw]

Sounds super good!

Something that could be (but is not strictly required) added on top is simplifying sending of the initial remark.
I'm not sure how other services index multisigs like that, but I can imagine it's based on whatever activity on a chain, including such remark. Hence the idea.

[Tbaut]

That remark, is only needed to let the indexer know that the multisig exists. Without this, I'd have to use a DB (as in a permissioned DB), and any other tool looking at the blockchain would not be able to know.
So when you create a multisig, a tx is created with a remark. The truth is that this tx doesn't need to be signed by all signatories, it can be rejected right away, it's just there to tell the indexer there's a multisig. My idea is to keep things simple, I didn't want to start having some kind of protocol based on remarks or anything. So for a first time creation, I'll keep this remark, and just add a trick in the indexer to replicate it across system chains.