Pingen2sdk

Added
* nothing

Improved / Changed
* nothing

Fixed
* version was not updated correctly before releasing 0.5.0

Added
* new sent and undeliverable letter event endpoints

Improved / Changed
* changed issues letter event endpoint to new url

Fixed
* nothing

Added
* webhook & incoming webhook management

Improved / Changed
* renaming methods

Fixed
* nothing

Added
* nothing

Improved / Changed
* nothing

Fixed
* version was not updated correctly before releasing 0.3.0

Added
* nothing

Improved / Changed
* covered last remaining lines in tests

Fixed
* github actions were throwing warnings