license_by_id retrieves the metadata for a set of licenses
with particular license IDs.
the ID (or IDs! It's vectorised!) to retrieve metadata for.
IDs can be extracted from existing data with
arguments to pass to httr's GET.
a list of licenses and their metadata (themselves in the form of
lists) which can be provided to other functions such as
# Get the GPL's metadata gpl_2_metadata <- license_by_id("GPL-2.0")