• Bumped minimum Go version to 1.18.
• Added omitempty for a bunch of fields in response structs to make them more usable for server implementations.
• Added util.RandomToken to generate GitHub-style access tokens with checksums.
• Added utilities to call the push gateway API.
• Added unread_notifications and MSC2654 unread_count fields to /sync response structs.
• Implemented MSC3870 for uploading and downloading media directly to/from an external media storage like S3.
• Fixed dbutil database ownership checks on SQLite.
• Fixed typo in unauthorized encryption key withheld code (m.unauthorized -> m.unauthorised).
• Fixed MSC2409 support to have a separate field for to-device events.