Prevent Submit Solutions Twice

[dusmart]

Solutions can be deployed multiple times and have the same id (same creationcode with params && same salt && same deploy address) while the runtimecode can be changed. See create2 for more details especially the Warning part.

Therefore, we'd better prevent someone from submitting twice. A simple record for submitting before deployment should be ok.

contracts/contracts/EulerDAO.sol

Lines 42 to 44 in 911357e

	function submit_code(bytes memory code) external {
	Create2Upgradeable.deploy(0, 0, code);
	}