Consider reverting module installation calls when state is not set (instead of no op)

[Amxx]

This issue is about

openzeppelin-community-contracts/contracts/account/modules/ERC7579Signature.sol

Lines 41 to 45 in 0e71ce5

	function onInstall(bytes calldata data) public virtual {
	if (signer(msg.sender).length == 0) {
	setSigner(data);
	}
	}

Basically we have three option if onInstall is called when a signer is already present:

• revert
• override storage
• no op (current behavior)

I'm worried about the choice of the last option, because the installer may expect the signer passed through the argument to be valid. Doing a no op here may cause an issue to be unnoticed.

I would propose something like

    function onInstall(bytes calldata data) public virtual {
        bytes memory currentSigner = signer(msg.sender);
        require(currentSigner.length == 0 || currentSigner.equal(data), Something());
        setSigner(msg.sender, data);
    }