In Id49201957e716ef8a2ea930b3616ca4fe6e35633 a breaking change was made to switch Language's optional value from null to false and to require the type Language.

When this broke the Minerva skin (which was still setting optional value to null) a follow up Ic43573a5598ebccfb2c525e3bdf48d0d467ef272 proposed that we make the Language option a required parameter to remove usages of globals with potential side effects (localisation should be the default). Given, optional parameters should be at the end of the function signature, this poses the question of whether the tooltip should also be optional or the parameter order should be changed (and update the hook execution that makes use of it).

After some discussion on both patches and the eventual reverting of the original patch, if done again this needs to follow the MediaWiki deprecation policy despite Minerva being the only consumer.