- Add BackupCredentialType to BackupAuthCredential, and rename the
members of BackupLevel. This is a **breaking change**: old
credentials will no longer work, and client and server have to
agree on the credentials being used. BackupAuthCredential also
now uses the "new" key derivation for the backup ID.
- MessageBackupKey now supports the "new" key derivations using an
"account entropy pool" string, as well as from a backup key and ID.
The "old" derivation from a "master key" has been deprecated in all
languages and will be removed in a future release.
- The backup validator now requires a mediaRootBackupKey in the
BackupInfo proto.
- Provide additional information on CDSI errors.
- swift: Initial audit for Sendable.
- Rust: Update boring to signal-v4.9.0b to fix build with newer
LLVM/libclang.
