comment to avoid future confusion about canvadoc model.
comment to avoid future confusion about canvadoc model.

test plan:
- make sure comments are there.
- make sure stuff works.

Change-Id: I51cd0af0c03b8b804976a1f90a1168dbe065220b
Reviewed-on: https://gerrit.instructure.com/153020
Reviewed-by: Daniel Lee <cf722ebef997381e7a050a89edd2d4ff7bce2601@instructure.com>
Product-Review: Caleb Guanzon <54fa1f30d451e4f3c341a8f3c47c9215fd0be9c6@instructure.com>
QA-Review: Caleb Guanzon <54fa1f30d451e4f3c341a8f3c47c9215fd0be9c6@instructure.com>
Tested-by: Jenkins

sfu/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms