Create service for viewing review assigments

[mkimberlin]

As a Manager, I want to view a list of all my review assignments so that I can stay on top of who needs to be reviewed.

Acceptance Criteria:

• The service allows a GET request to an endpoint like /reviews/assignments/${reviewPeriodId} with a optional query parameter reviewerId
• If no reviewerId are provided, the service returns a list of all review assignments for the review period whose ID is provided in the path.
• If a reviewerId is provided, the service returns a list of assignments where the reviewerID matches.
• The service can only be called if the current user has the CAN_VIEW_REVIEW_ASSIGNMENTS permission (must be created)
• If no assignments exist for the review period, then a set of default review assignments should be returned:
  • The default review assignments should include every current employee (as reviewee).
  • Each employee should have their supervisor assigned as their default reviewer.
  • The default assignments should not have been persisted, and should not have IDs (some employees may, ultimately, not be included in a review period)
• Each returned assignment object includes:
  • id: The unique identifier for the assignment (if not providing default assignments).
  • 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 this assignment relates to.
  • approved: A boolean indicating if the review has been approved (true) or not (false).