Breaking changes:

• New toFormData helper function that allows the implementor to pass an object and allow axios to convert it to FormData (#3757)
• Removed functionality that removed the the Content-Type request header when passing FormData (#3785)
• (*) Refactored error handling implementing AxiosError as a constructor, this is a large change to error handling on the whole (#3645)
• Separated responsibility for FormData instantiation between transformRequest and toFormData (#4470)
• (*) Improved and fixed multiple issues with FormData support (#4448)

QOL and DevX improvements:

• Added a multipart/form-data testing playground allowing contributors to debug changes easily (#4465)

Fixes and Functionality:

• Refactored project file structure to avoid circular imports (#4515) & (#4516)
• Bumped follow-redirects to ^1.14.9 (#4562)

Internal and Tests:

• Updated dev dependencies to latest version

Documentation:

• Fixing incorrect link in changelog (#4551)

Notes:

• (*) Please read these pull requests before updating, these changes are very impactful and far reaching.