Remove the approved and disapproved status' from applications

[dakaza98]

Some positions are applied via FUM and therefor get the status approved or disapproved. However, these statuses are barely used and only act as a unnecessary middle step. We will therefor remove these statuses and just use appointed and turned down.

The new flow will therefor become submitted -> appointed or turned down for all applications.

A migration has to be made for this that changes the status of the current applications. It should change like this:

• Approved -> Submitted
• Disapproved -> Turned down