This link used to open in a new window, and we accidentally changed that
behavior while refactoring it in commit c2710de5f.
Since we're adding a test for this case, and the Proposals::NewComponent
class is similar, we're adding a test for that class too. In the case of
proposals, we need to sign in a user because the proposals form contains
fields to attach image, that currently rely on a user being signed in.