R1:f15ed36d3c23

legalpad schema

Summary:
Ref T3116. This is a large amount of schema for V0 but it seems relatively complete to the desired features in T3116.

The only thing of note that is missing is documentSignatures should have some sort of "signedStatus". "Un-signing" seemed weird to me, though I could imagination "pending signature". "Pending signature" could be done via edges pretty easily.

Plan is to have "Document" be at the top level and own policy. "DocumentBody" will store a version of title and text for…