SwA Profile Comments

lines 152-154 explain that MIME Headers must be canonicalized, but does not
provide an algorithm for doing so.

lines 161-166 explain that MIME Part canonicalization algorithms are
dependant on the content-type, but does not explain how to find the details
for any content-types.

lines 197-203 explain that digests are computed over MIME Parts after
decoding any Content-Transfer-Encoding, but it is unclear whether you can
sign the Content-Transfer-Encoding header itself.

Thanks,
Mike