If an user is saving their bitcoins on Electrum and an contentious fork happens, what determines what end of the chain will be followed? Does it all comes down to what the developers want to do with the software?

Shouldn't a system be developed that tells you a fork happened and lets you what chain to follow, or could this end in a total mess?

This is why I have never liked SPV wallets, you are the mercy of someone else when these things happen.