Operation without TWCs

[MikeBishop]

@ngardiner, I'm thinking about how to approach non-TWC-based charging. That would let us support people with Gen3 TWCs, people using mobile connectors, people using third-party EVSEs, etc.

I'm inclined to take the current TWC class and abstract it to an interface which could be implemented by multiple different types of underlying hardware, similar to the EMS interface. Then the Tesla API can simply implement that interface for each vehicle. (Down the road, that model might open the door to multiple TWCManager instances exposing their TWCs as read-only instances to each other, though that's not my first priority.)

The biggest challenge (i.e. code I don't know) is two-fold:

• Making TWCManager not die when a serial interface isn't found
• What drives the event loop if messages aren't coming in from TWCs? Currently, I think all activity is in response to received heartbeat messages.

I'm sure that there are generic Python timer-based event loops I can pull in, but I wouldn't be surprised if there are footguns I'm not aware of in such a big lift.

I'll also need to de-duplicate vTWCs from the Tesla API and physical TWCs; presumably by VIN, at least initially. (I have some ideas for ways to verify the connected car if the TWC doesn't support VIN reports, but I don't want to get into that arcana if I don't have to.)

I'm going to have some focus time available around the start of November and was planning to look at it more closely then. Please add any thoughts or suggestions here for me to have on hand when I start in.

[MikeBishop]

Also, how not to break modes other than fakeMaster, since I never use them. ;-)