Using `have_current_path`, Capybara waits until the condition is true,
while using `include` the expectation is evaluated immediately and so
tests might fail when using a driver supporting JavaScript.
Besides, using `have_current_path` the error message is more readable
when the test fails.
We were repeating the same code over and over (with a few variants) to
setup tests which require an administrator. We can use a tag and
simplify the code.
