Added test to make sure admin flag is not accessible
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Added tests to make sure signed-in-only links don't show to non-signed-in users
also tested by visiting a static page
refactored new and edit templates to share a partial for the form
Some exercises

- Refactored new.html.erb and edit.html.erb to use a shared partial
- Prevent signed-in users from doing User#new or User#create
test that friendly forwarding is only for one sign-in, not subsequent sign-ins
Prevent admins from deleting themselves