v0.50.3

This release updates frame-decode to 0.18.1, which fixes V5 signer payload construction and improves how authorization extensions (like VerifyMultiSignature) are handled.

Fixed

• V5 signer payloads now correctly include the transaction extension version and call data as an immutable base implication, matching FRAME's transaction extension pipeline semantics. (paritytech/frame-decode#104)
• Unknown Option<T> transaction extensions are now encoded as None (0u8) by default, allowing transaction encoding to succeed on chains with optional extensions. (from frame-decode 0.17.2)

Changed

• VerifySignature now uses is_authorization_extension to declare itself as an authorization boundary, replacing the previous out.clear() side effects in encode_value_for_signer_payload_to and encode_implicit_to. (#2268, #2269)
• Update frame-decode from 0.17.1 to 0.18.1. (#2268)