Also simplify the @covers annotations while we are here. The class
is really simple. There isn't much that can be covered acidentally.
Change-Id: I105f4ea6d6beb119d1557a32b691e9eda1b8085c
PHP classes and test are somewhat copies from the Popups codebase.
Some refactoring was applied. More could be done. Not to sure if
this should happen more in follow ups though.
Could also reduce the complexity of checks on the JS side. Most of
these things can only change on page load. The only dynamic part
left is the anon user setting managed by the Popups extension.
Note, that I needed to add a new PHP config for here although the
other still exists and is needed in the Popups extension. This
will change, when the user settings code also moves.
I guess it's okay for now though. Both settings default to true
and are not overridden in the config repos.
Also needed to add the Gadget extension as phan dependency.
Bug: T362771
Depends-On: Ia028c41f8aaa1c522dfc7c372e1ce51e40933a5e
Change-Id: Ie6e8bc706235724494036c7f0d873f5c996c46e6
