UniswapV2Pair: initialize function should be protected

[Maksandre]

🐞 Bug Report

💻 Describe the bug

initialize function has a public modifier and does not contain any checks inside its body. This means anyone can call this function externally leading to token addresses override.

uniswap-v2-nil/contracts/UniswapV2Pair.sol

Lines 55 to 60 in 3ede108

	function initialize(address _token0, address _token1, CurrencyId _tokenId0, CurrencyId _tokenId1) public {
	token0 = _token0;
	token1 = _token1;
	tokenId0 = _tokenId0;
	tokenId1 = _tokenId1;
	}

Additionally, the Factory should call this function, which is not happening now.