Fix model for rooms and assistants on request table

- Fixes rooms by only showing rooms used in the list of current labs.
- Fixes courses by only showing courses from current labs.
- Fixes assistants in the model by adding them to the model.

src/main/java/nl/tudelft/ewi/queue/model/Course.java

@@ -184,6 +184,13 @@ public class Course implements Serializable {
 				.collect(Collectors.toList());
 	}
 
+	public List<User> getRequestHandlers() {
+		return roles.stream()
+				.filter(r -> r instanceof Assistant || r instanceof Manager || r instanceof Teacher)
+				.map(Role::getUser)
+				.collect(Collectors.toList());
+	}
+
 	public List<User> getAssistants() {
 		return roles.stream()
 				.filter(r -> r instanceof Assistant)

src/main/java/nl/tudelft/ewi/queue/service/RequestTableService.java

@@ -172,7 +172,7 @@ public class RequestTableService {
 						}));
 
 		// Add the created model attributes
-		addToModel(model, courses, activeLabs, filteredRequests, filters);
+		addToModel(model, activeLabs, filteredRequests, filters);
 		model.addAttribute("queued", queueCount);
 	}
 
@@ -203,7 +203,8 @@ public class RequestTableService {
 		List<Course> courses = user.getParticipates();
 		List<Lab> labs = labs(courses);
 
-		List<Group> groups = courses.stream().filter(Course::getHasGroups)
+		List<Group> groups = courses.stream()
+				.filter(Course::getHasGroups)
 				.flatMap(c -> c.getGroups().stream())
 				.filter(g -> g.hasMember(user))
 				.collect(Collectors.toList());
@@ -217,30 +218,47 @@ public class RequestTableService {
 				(currentGroup.or(currentUser)).and(predicate), pageable);
 
 		// Add the created model attributes
-		addToModel(model, courses, labs, filteredRequests, filters);
+		addToModel(model, labs, filteredRequests, filters);
 	}
 
 	/**
 	 * Adds the given information to the model using the variable names used in the "request/list.html" page.
 	 *
 	 * @param model    The model to The model to add attributes to.
-	 * @param courses  The courses that should be displayed in filters.
 	 * @param labs     The labs that should be displayed in filters.
 	 * @param requests The requests that should be displayed on the page.
-	 * @param filters  The state of the page.
+	 * @param filters  The state of the filters.
 	 */
 	private void addToModel(Model model,
-							List<Course> courses,
 							List<Lab> labs,
 							Page<Request> requests,
 							Object filters) {
-		addDefaultModelAttributes(model);
+		List<Room> rooms = labs.stream()
+				.flatMap(lab -> lab.getRooms().stream())
+				.distinct()
+				.collect(Collectors.toList());
+
+		// Fetch the courses from the given list of labs to make sure only currently active
+		// or relevant courses are shown.
+		List<Course> courses = labs.stream()
+				.map(Lab::getCourse)
+				.distinct()
+				.collect(Collectors.toList());
+
+		List<User> assistants = courses.stream()
+				.flatMap(course -> course.getRequestHandlers().stream())
+				.distinct()
+				.collect(Collectors.toList());
+
 		model
+				.addAttribute("rooms", rooms)
+				.addAttribute("requestTypes", requestTypeRepository.findAll())
 				.addAttribute("courses", courses)
 				.addAttribute("activeLabs", labs)
 				.addAttribute("requests", requests)
 				.addAttribute("state", filters)
-				.addAttribute("assignments", assignments(labs));
+				.addAttribute("assignments", assignments(labs))
+				.addAttribute("assistants", assistants);
 	}
 
 	/**
@@ -265,17 +283,6 @@ public class RequestTableService {
 				.orElse(new LinkedMultiValueMap<>());
 	}
 
-	/**
-	 * Adds the attributes that can be filled in without context of the request table view to the given Model.
-	 * These attributes can be rooms and requestTypes because we simply select all of them.
-	 *
-	 * @param model The model to add attributes to.
-	 */
-	private void addDefaultModelAttributes(Model model) {
-		model.addAttribute("rooms", roomRepository.findAllByOrderByNameAsc());
-		model.addAttribute("requestTypes", requestTypeRepository.findAll());
-	}
-
 	/**
 	 * Flatmaps a list of courses to a list of labs.
 	 *