Remove items from payload dictionary if their value is None

[Esterni]

Create class method from following code-block and apply to all functions so that they are removed from the URL query when sent to iRacing.

for key in payload.copy():
            if payload.get(key) is None:
                del(payload[key])
            else:
                pass

Functions need to be tested for proper functionality afterwards. It is known that a value of -1 is equal to the key being set to nothing key= but it is unknown if queries will still work if the key is removed entirely.

[Esterni]

Confirmed for event_results() that removing raceweek= did not affect results. (This was an endpoint that had raceweek= in the URL query when using iRacing's "My Results" page)