**User Story:** - As a Deppy user, I would like to provide Deppy a list of constraints and Entity Sources and be returned a solution set consisting of entity IDs. **Acceptance Criteria:** - If a solution set is found, the list of entity IDs are returned. - If no solution set is found, an error explaining why the constraints could not be met is returned. - The operator CR's status is updated to reflect that an entity satisfying it's constraints have been found.