Resolve "[Queue-2.0] CSV Import for TAs"

What does this mr do?

Allow teachers to upload a CSV file with "netId","role" into queue to add several students, ta's etc.

Screenshots

before

after

Error gets displayed when there is something wrong with the CSV

Does this MR meet the acceptance criteria?

• I have added a changelog entry to reflect the significant changes I made.
• Tests were created to test the feature.
• I have updated the documentation accordingly.
• I adhere to the style guide. Closes #396 (closed)

Note: A redo after messing up !436 (closed)

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

@@ -304,6 +304,15 @@ public class EditionController {
 		return "redirect:/edition/" + editionId + "/participants";
 	}
 
+	/**
+	 * Adds new participants to the course based on a CSV file that was uploaded by the user.
+	 *
+	 * @param  editionId  The id of the edition to which the users must be added.
+	 * @param  csv        A CSV file containing both the netId and their role in the course.
+	 * @param  attributes Used to pass information when redirecting to Thymeleaf.
+	 * @return            A redirect to either the participants page when successfull, otherwise redirect ot
+	 *                    create participants page
+	 */
 	@PostMapping("/edition/{editionId}/participants/import")
 	@PreAuthorize("@permissionService.canManageTeachers(#editionId)")
 	public String importParticipants(@PathVariable Long editionId,