* [chore] Remove years from all license headers
Years or year ranges aren't required in license headers. Many projects
have removed them in recent years and it avoids a bit of yearly toil.
In many cases our copyright claim was also a bit dodgy since we added
the 2021-2023 header to files created after 2021 but you can't claim
copyright into the past that way.
* [chore] Add license header check
This ensures a license header is always added to any new file. This
avoids maintainers/reviewers needing to remember to check for and ask
for it in case a contribution doesn't include it.
* [chore] Add missing license headers
* [chore] Further updates to license header
* Use the more common // indentend comment format
* Remove the hack we had for the linter now that we use the // format
* Add SPDX license identifier
* create visibility filter for boostability and allow self-boosting for any visbility but direct messages
* add a followers-only status to local_account_2
* fix typo in comment
* add license header, unwrap errors, be explicit about non-boostable visibility settings to avoid rogue boosting from miscoded clients, use ID compare for checking if self-boosting
* add tests for statusboostable filter
* fix tests that were affected by adding a new status to the test data
* fix the rest of tests affected by adding a status to the textrig data
