* Add new table and model
* Store banned user username hash on delete
* Prevent previously banned user from signing up again
* Update method name
* Refactor code and add more specs
* Test improvements
* Don't override existing global flash
* Fix typo
* Update spec description
* Update schema.rb
* More schema.rb fixes
* Simplify spec
* Update migration
* Clean up migration
* Rename method
* Add DataDog counter
* Revisit error handling
* Remove spurious empty line
* Make model name more explicit