Rewrite webhook parser

[JayJay1989]

This pull request will change:

• Make the parser static
• Adds comments
• Makes EventTypes an Enum
• Bump Test project to use .net 5
• Bump Dependencies
• Add a properly error when a webhook event is not known
• All changes from branch features/add-new-event-types

Checks are done through Enum parsing.

[Hinni]

Hi @JayJay1989. Thanks for your contribution. I will check it asap. Cheers