Resolve "Make assignment with modules endpoint."

What does this MR do (summary)?

See #154 (closed) for desc.

What changes have you made (detailed)?

1.) Added an endpoint to fetch the necessary information 2.) Added tests

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.

Closes #154 (closed)