improv: add booker system + trainline booker

[f-hj]

Hi Tousset! 👋

This adds an auto-booking feature that allows the bot to automatically book a train if the train has seats available (currently the first train available between the minHour and maxHour). This PR introduces some terminologies:

• booker is a component that can search and book train (it was a crawler before)
• book value in travel to check if the trip should be automatically booked

It adds the Trainline search and booking system. Note that this one uses the Trainline business API, because this one is much easier to reverse than the public one and is completely free of charge.

I plan to add something like a CronTravel to automatically create a Travel for a specified date (e.g.: every tuesday at 7 I want to travel from A to B), wdyt?

Waiting for your review

[Eywek]

I plan to add something like a CronTravel to automatically create a Travel for a specified date (e.g.: every tuesday at 7 I want to travel from A to B), wdyt?

lgtm