R1:c8d20d3c66f2

Phriction - policy front end changes

Summary:
Ref T4029. Fixes T6034.

Various front-end miscellania here. See D10814#96251. This more or less makes policy work but I am not going to call it "fixed" here since we need D10814 to be deployed too and will do that manually.

Test Plan:
- changed document policy from web ui and changes persisted
- changed document policy from web and had form error and changes persisted
- created a structure like users/users/justmyuserpolicy and made sure another user could…