Previously set hooks or ISMs cannot be unset, so contracts can't opt back into using the default hook / ISM

[tkporter]

Background

The ConnectionMsg::SetIsm message only lets you set a new ISM, and same for ConnectionMsg::SetHook: https://github.com/many-things/cw-hyperlane/blob/4f5656d4704178ac54d10467ca7edc3df2312c4b/packages/connection/src/lib.rs#L51-L68

The implication of this is that getting the ISM or Hook will only return None (indicating to use the default hook or ISM configured on the Mailbox) if it hasn't been set before: https://github.com/many-things/cw-hyperlane/blob/4f5656d4704178ac54d10467ca7edc3df2312c4b/packages/connection/src/lib.rs#L72-L100

Which means that any contract using connection that has previously set an ISM or Hook won't be able to opt back into using the default ISM or Hook.

Required Criteria

• [ ] ConnectionMsg::SetIsm accepts an Option, where None unsets the ISM and opts the contract back into using the default ISM
• [ ] ConnectionMsg::SetHook accepts an Option, where None unsets the hook and opts the contract back into using the default hook

Appendix