For the most part having a bent iPhone is considered to be accidental damage. There really isn't any way it's considered a manufacturing defect covered under warranty. Apple won't actually repair it. A bent case would likely require a full out of warranty replacement. It's $319+tax for the iPhone 7.
If you have Squaretrade, pay the deductible and get a replacement. Otherwise, what was the point of buying insurance? If you want to upgrade, then sell the replacement 3rd party.
As for a case, all that I've used will flex. If the case will flex, how would it protect your device from bending? You'd need a heavy, solid metal case to protect the phone from being bent, which is not practical.
Question: can you fix a bent iphone 7?