pub fn encrypt_file(
plaintext: &[u8],
room_crypto: &mut RoomCrypto,
) -> Result<(Vec<u8>, EncryptedFileMeta)>Expand description
Encrypt plaintext with a fresh ChaCha20-Poly1305 key, then Megolm-
wrap that key via the room’s outbound session. The returned bytes
are what gets chunked and sent on the wire; the meta travels in the
FileOffer alongside the file_id.