Measure Metadata: e2e functional
Merge branch 'MayRelease' of https://github.com/RareCrowds/OpenAdStack into MayRelease
New User: Add missing POST body for invites
Delivery Networks: Internal system properties + cleanup
 * Move internal use only properties to system properties
 * Include back-compat with existing properties
 * Fix system property setter to replace existing non-system properties
 * Add unit tests for roundtrips and upgrades
 * Add streamlined entity creation test helpers