Fix issues with bonus xp

[thortol]

Description

Resolves #1168, #1170.

Some issues with the code and fixes the bug where autograded assignments do not have bonus xp awarded. The bug is fixed by updating bonus xp when grading is published.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Code quality improvements

Checklist

• I have tested this code
• I have updated the documentation

[coveralls]

coverage: 94.372%. remained the same
when pulling 429aad4 on thortol:fix-issues-with-bonus-xp
into c0d95e9 on source-academy:master.