Previously the return to forum link would automatically take you to the
forum homepage, however this was not intended functionality. We should
attempt to take the user to their last viewed forum page.
This change fixes a bug in how we determined what the destination link
should be.
Internal ref: /t/110508
This could happen after you had already change the separation mode and would cause unexpected bugs.
This PR also adds more tests around using switch buttons with chat.
This commit ensures we have correct icon and title on mobile for the chat header icon.
It also fixes a bug where the site setting was not correctly used when the user has not yet set the user option.
Both cases are now correctly tested.