Add flake8-bandit linting (#156)

The linter has been used in the past, so most assertions for these were
already there but needed to be updated to use `noqa: S` instead of
`nosec: B` annotations.

fastapi_cache/coder.py

@@ -128,7 +128,7 @@ class PickleCoder(Coder):
 
     @classmethod
     def decode(cls, value: bytes) -> Any:
-        return pickle.loads(value)  # nosec:B403,B301
+        return pickle.loads(value)  # noqa: S301
 
     @classmethod
     def decode_as_type(cls, value: bytes, *, type_: Optional[_T]) -> Any: