Bencoding is changed to use a string pattern instead, for a few reasons:
bencoding maps is non deterministic because we can't guarantee the order of the fields, which means the signature check fails
the bencoding standard wraps the map into starting with d and ending in e. to respect bep44 requirements, we need to remove the first and last byte
we only and always will have 2 fields here and bencoding results in a .. string. so, might as well use a string template to create the payload for signing
Bencoding is changed to use a string pattern instead, for a few reasons: