Resolve "Endpoints for importing grades"

What does this MR do (summary)?

• Closes #121 (closed)
• Adds grade import endpoints
• Adds endpoints for getting all submissions by assignment and module
• Fixes a bug where Submission was not properly mapped to SubmissionDetailsDTO

Does this MR meet the acceptance criteria?

• The main application was run to make sure the server still runs without errors.
• Tests were written to verify the behaviour of this code.
• Javadoc and other comments were added to make the code understandable.
• The code adheres to the style guidelines.

src/main/java/nl/tudelft/labracore/controller/GradeController.java

@@ -19,6 +19,7 @@ package nl.tudelft.labracore.controller;
 
 import javax.transaction.Transactional;
 
+import nl.tudelft.labracore.dto.create.GradeBatchImportDTO;
 import nl.tudelft.labracore.dto.create.GradeCreateDTO;
 import nl.tudelft.labracore.dto.id.PersonIdDTO;
 import nl.tudelft.labracore.dto.patch.GradePatchDTO;
@@ -26,6 +27,7 @@ import nl.tudelft.labracore.model.Grade;
 import nl.tudelft.labracore.model.Person;
 import nl.tudelft.labracore.repository.GradeRepository;
 import nl.tudelft.labracore.security.user.AuthenticatedPerson;
+import nl.tudelft.labracore.service.GradeService;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.security.access.prepost.PreAuthorize;
@@ -37,6 +39,8 @@ import org.springframework.web.bind.annotation.*;
 public class GradeController {
 	@Autowired
 	private GradeRepository gr;
+	@Autowired
+	private GradeService gs;
 
 	/**
 	 * Adds a grade by processing the sent grade creation object.
@@ -68,4 +72,17 @@ public class GradeController {
 		patch.setGradedBy(new PersonIdDTO(grader.getId()));
 		return patch.apply(gr.findByIdOrThrow(id)).getId();
 	}
+
+	/**
+	 * Imports a batch of grades.
+	 *
+	 * @param gradeImport The import with all the grades.
+	 */
+	@PatchMapping("import/{assignmentId}")
+	@PreAuthorize("hasAuthority('GRADE_UPDATE')")
+	public void importGrades(@PathVariable Long assignmentId, @RequestBody GradeBatchImportDTO gradeImport,
+			@AuthenticatedPerson Person grader) {
+		gs.importGrades(assignmentId, gradeImport, grader);
+	}
+
 }