URITemplate rather than our own
AtomDate for date formatting and parsing rather than our DateUtil
ResponseContext that streams collection details
EntityProvider or ContentProvider or maybe both (how do they relate?)
StandardDavRequest and StandardDavResponse available to security filter as well as servlet
DavAccessDecisionManager operate on DavResource rather than directly on Item and User
ls on /dav/users/ shows 404 for each member resource
PROPFIND requests made by ticketed users (i.e. properties that should only be exposed to the resource's owner)?