Similar to how `engineio` provides a JSON-compatible module, this change
adds a custom JSON encoder with support for additional types.
Changing SocketIO's JSON module fixes the encoding issue when the
scanning process tried to send a datetime, failing and the frontend not
displaying the scanned game (commonly, when it had sibling games)
This change replaces the creation of Redis URL, from a simple string
interpolation, to using `yarl.URL`. The main benefit, besides not
forgetting to set all five different variables on every Redis client
initialization, is that user credentials are correctly URL-encoded, if
present.
Up until now, if a password had special characters, it could break the
generated URL.
This change also introduces support for a `REDIS_SSL` setting, which
allows the user to specify if the Redis connection should use SSL or not.
