Prevent enqueueing without a group if groups are required

src/main/java/nl/tudelft/queue/controller/AssignmentController.java

@@ -18,10 +18,8 @@
 package nl.tudelft.queue.controller;
 
 import nl.tudelft.labracore.api.AssignmentControllerApi;
-import nl.tudelft.labracore.api.dto.AssignmentCreateDTO;
-import nl.tudelft.labracore.api.dto.EditionDetailsDTO;
-import nl.tudelft.labracore.api.dto.ModuleDetailsDTO;
-import nl.tudelft.labracore.api.dto.ModuleSummaryDTO;
+import nl.tudelft.labracore.api.StudentGroupControllerApi;
+import nl.tudelft.labracore.api.dto.*;
 import nl.tudelft.queue.cache.AssignmentCacheManager;
 import nl.tudelft.queue.cache.EditionCacheManager;
 import nl.tudelft.queue.cache.ModuleCacheManager;
@@ -50,6 +48,9 @@ public class AssignmentController {
 	@Autowired
 	private AssignmentControllerApi aApi;
 
+	@Autowired
+	private StudentGroupControllerApi sgApi;
+
 	/**
 	 * Gets the page for creating an assignment. This is a basic page with only the most basic of properties
 	 * for an assignment. Further adjustments or creation options should be made available in Portal or later
@@ -141,6 +142,24 @@ public class AssignmentController {
 		return "redirect:/edition/" + module.getEdition().getId() + "/modules";
 	}
 
+	/**
+	 * Get the page with a list of groups to join for an assignment.
+	 *
+	 * @param  assignmentId The id of the assignment
+	 * @return              The group page
+	 */
+	@GetMapping("/assignment/{assignmentId}/groups")
+	public String getAssignmentGroups(@PathVariable Long assignmentId, Model model) {
+		AssignmentDetailsDTO assignment = aCache.getRequired(assignmentId);
+		ModuleDetailsDTO module = mCache.getRequired(assignment.getModule().getId());
+
+		model.addAttribute("module", module);
+		model.addAttribute("edition", eCache.getRequired(module.getEdition().getId()));
+		model.addAttribute("groups", sgApi.getAllGroupsInModule(module.getId()).collectList().block());
+
+		return "module/groups";
+	}
+
 	/**
 	 * Adds attributes for the create assignment page to the given model.
 	 *