v0.18.0-beta.1

• Bumped minimum Go version to 1.21.
• (bridge) Bumped minimum Matrix spec version to v1.4.
• Breaking change (crypto) Deleted old half-broken interactive verification code and replaced it with a new verificationhelper.
  • The new verification helper is still experimental.
  • Both QR and emoji verification are supported (in theory).
• (crypto) Added support for server-side key backup.
• (crypto) Added support for receiving and sending secrets like cross-signing private keys via secret sharing.
• (crypto) Added support for tracking which devices megolm sessions were initially shared to, and allowing re-sharing the keys to those sessions.
• (client) Changed cross-signing key upload method to accept a callback for user-interactive auth instead of only hardcoding password support.
• (appservice) Dropped support for legacy non-prefixed appservice paths (e.g. /transactions instead of /_matrix/app/v1/transactions).
• (appservice) Dropped support for legacy access_token authorization in appservice endpoints.
• (bridge) Fixed RawArgs field in command events of command state callbacks.
• (appservice) Added CreateFull helper function for creating an AppService instance with all the mandatory fields set.