Adopt Drupal's Token API for Guest Messages

Problem/Motivation

The bee_hotel module currently implements its own token system for guest messages. Tokens are defined in YAML files under config/guest_messages and replaced with a simple str_replace() call. While functional, this approach bypasses Drupal's native Token API and isolates BeeHotel tokens from the rest of the Drupal ecosystem.

Guest messages are one of the most valuable features of BeeHotel for small hospitality businesses. A B&B owner or a small hotel manager can prepare a message template once — a booking confirmation, a pre-arrival welcome, a check-out reminder, a review request — and have it automatically personalised for every guest with their name, booking number, room, dates, balance due, and bank details. No manual copy-paste, no risk of sending the wrong guest the wrong dates. Examples of everyday use cases:

• Booking confirmation. "Dear [guest name], thank you for your booking no. [booking number]. Your arrival is expected on [arrival date], room [room name], total [total amount], balance due [balance]." Sent automatically in the guest's language.
• Pre-arrival welcome. "We look forward to welcoming you on [arrival date]. Check-in is available from [checkin time]. Here are the directions and the Wi-Fi password."
• Balance reminder. "Your balance of [balance] is due by [balance due date]. Bank details: [bank details]."
• Check-out reminder. "Check-out is by [checkout time] on [checkout date]. Thank you for staying with us."
• Post-stay review request. "Dear [guest name], we hope you enjoyed your stay in [room name]. Would you leave us a review?"

These messages are sent by email or WhatsApp directly from the order page, in the guest's own language, with attachments and useful links (maps, directions, house rules). This is what makes BeeHotel usable by non-technical property owners: they write the message once, in plain language, and BeeHotel fills in the details for each guest.

However, the current token system — described in the next paragraph — limits this value. Because BeeHotel tokens are not registered with Drupal's Token API, they cannot be used outside the guest-message context, they cannot be chained with entity tokens, and they cannot be picked up by other modules or by the standard token browser. Aligning BeeHotel with the standard Token API would make guest messages more powerful, more reliable, and easier to extend for the property owner.

Proposed resolution

Migrate the guest-message token layer to Drupal's standard Token API.

1. Define token types and tokens via hook_token_info() (or the #[Hook] attribute in Drupal 11.2+).
2. Implement replacement logic in hook_tokens(), using $bubbleable_metadata to declare cache dependencies.
3. Replace the custom str_replace() loop in BeeHotelGuestMessageTokens::applyTokens() with \Drupal::token()->replace().
4. Keep the YAML files only for message templates, removing them from the token definition role.

This change can be rolled out progressively: new standard tokens can coexist with the legacy [token_id] syntax until all stored messages are migrated.