Message signatures per identity

[NoraCodes]

Would it be possible to add message signatures for each identity? E.g., when I start a new message and pick an identity, it would autofill the signature at the bottom:

Message message, message message

---
Signature

So you could remove it if you wanted for each individual message. I'd be happy to implement this if someone could clarify to me how identities are stored.

[PeterSurda]

I want to have this later in the new UI.