Using `<a>` tags with no `href` means these elements cannot be activated
by keyboard users, so we're replacing them with buttons.
In the future we probably want to add more consistency so all toggle
buttons use the same code. We might also add styles depending on the
`aria-expanded` property.
The main obstacle to extract this partial was probably the paths for the
flag and unflag actions.
Now that we use Rails 5.1 `resolve` method to handle nested resources,
we can use `polymorphic_path`.
Also note the code is a bit ugly because comments render a divider. We
should probably use a CSS border instead.
Co-Authored-By: taitus <sebastia.roig@gmail.com>