Create service for adding a review assignment

[mkimberlin]

As a Manager, I want to create review assignments for my employees so that I can easily track who needs to be reviewed.

Acceptance Criteria:

• The service allows a POST request to an endpoint like /reviews/assignments with a JSON body containing:
  • revieweeId: The ID of the employee being reviewed.
  • reviewerId: The ID of the employee conducting the review.
  • reviewPeriodId: The ID of the review period that the assignment is related to.
• The service creates a new review assignment with an initial approved status of false.
• The service can only be called if the current user has the CAN_CREATE_REVIEW_ASSIGNMENTS permission (must be created)
• The service returns a JSON response containing the details of the newly created assignment, including:
  • id: The unique identifier for the assignment.
  • revieweeId: The ID of the employee being reviewed.
  • reviewerId: The ID of the manager conducting the review.
  • reviewPeriodId: The ID of the review period that the review assignment relates to.
  • approved: A boolean indicating if the review has been approved (true) or not (false).