Resolve "AuTA feedback is not shown"

What does this MR do (summary)?

Closes #82 (closed)

What changes have you made (detailed)?

Caches are no longer used in Async methods as they are request bound. Also, automatic feedback is now saved before grade recalculation so students get feedback regardless of their module/edition grade being updated.

Does this MR meet the acceptance criteria?

• The main application was run to make sure the server still runs without errors.
• Tests were written to verify the behaviour of this code.
• Javadoc and other comments were added to make the code understandable.
• The code adheres to the style guidelines.