Undocumented microdescriptor 'directory-signature' field

Hi, the 'directory-signature' lines in microdescriptor consensus appear to have an extra undocumented field...

From section 3.3 (Vote and consensus status documents):

"directory-signature" SP identity SP signing-key-digest NL Signature

If this was any different for microdescriptor consensuses then it should say so in section 3.6.2 (Microdescriptor consensus).

Example from my cached-consensus...

directory-signature 14C131DFC5C6F93646BE72FA1401C02A8DF2E8B4 BF112F1C6D5543CFD0A32215ACABD4197B5279AD
-----BEGIN SIGNATURE-----
LcLgOFLh2Hb4ryZGmNH/v4fsptOi50rUawZEG/bJlWhQDmWIFJQ21Jg+Nj/99ltv
ybT5i1HEpWhKjz8N3iqtB90y+B+dJ/fbjHmIIGxG3TW7Q8zfsxQhjlAz+f1u47o6
dHnnylzcUjhjJ7w2ybaFSTIfVO9WPXuerF+ypIq3mn4=
-----END SIGNATURE-----

Example from my cached-microdesc-consensus...

directory-signature sha256 14C131DFC5C6F93646BE72FA1401C02A8DF2E8B4 BF112F1C6D5543CFD0A32215ACABD4197B5279AD
-----BEGIN SIGNATURE-----
jPDohv36PoXQIuxNNd2IYvj/RiDuJkIGhOkm5qD8yLXZiUfdcFYOt6Druvub1T8g
GRpvMsMJz+/clNggMzaynlqfN1UCZAykk8v6gnpYz1pqyfNS/J+3SlnhfeNr604s
iRB7VKis9lw/QX/U8cOQAFIhvAAdEZM7UGyhQ92ikbQ=
-----END SIGNATURE-----