Features:
- gRPC clients can now request a signed response by setting a non-zero 'nonce' on 'NativeCallItem' or 'NativeSubscribeRequest'. The reply carries the signature, key id, originating upstream and the nonce. Reuses the gRPC auth key ('server.grpc-auth.provider-private-key-path') - no new config - and labels signing-capable upstreams with 'secure-signed: "true"' (#317)
- TON: 12 indexer v3 methods added to the spec - traces, pendingTraces, pendingActions, pendingTransactions, decode, metadata, nft/sales, vesting, dns/records, multisig/orders, multisig/wallets. Previously any path missing from the spec was rejected with "method is not supported" before upstream selection, since upstream method sets are built from the same spec (#318)