Aligns the syntax with the rest of Task, and lets functions compose: a
Basic credential no longer needs its base64 computed by hand. The strict
expansion this replaces was already gone, so nothing is lost by the
switch.
Only functions resolve — the configuration file is read before any
Taskfile, so {{.VAR}} has nothing to read and produces an empty header.
That is documented next to the option.
bff4f97d7e