* disable NewCops
* update TargetRubyVersion
* Fix Lint/MissingSuper for ActiveModelSerializers::Model
* Fix Lint/MissingSuper for feed
* Fix Lint/FloatComparison
* Do not use instance variables
* Add structure for lists
* Add list timeline streaming API
* Add list APIs, bind list-account relation to follow relation
* Add API for adding/removing accounts from lists
* Add pagination to lists API
* Add pagination to list accounts API
* Adjust scopes for new APIs
- Creating and modifying lists merely requires "write" scope
- Fetching information about lists merely requires "read" scope
* Add test for wrong user context on list timeline
* Clean up tests
