Define the logic for permissions to see anonymous posters

[sophiefeng18]

Define the logic in codebase that only the admin can see the names of anonymous posters.

Estimated effort for each task: medium
Dependencies among tasks: #35 #24 #15
Milestones to indicate which sprint the issue should be completed in (Sprint 1, Sprint 2, Stretch): Sprint 1
Acceptance criteria that describes how you know this task is done - think about how you will test this feature: Write tests so code passes all the tests.