Fix submission result responses being too big or empty

Description

Fixes submissions returning most entities multiple times, leading to responses big enough to make Spring stop working once again.

Changes

• The submission controller returns entities instead of entity containers
• The getAllChildren getter is marked as @JsonIgnore so Jackson (which is the library that Spring uses) ignores the setter while serializing

Additions

None.

Test and Review

Closes #166 (closed)

To be filled in by the reviewers

• All of the methods are commented to expectation

• The methods are tested to satisfaction

• There are no unnecessary files present in the MR

• The continuous integration has no problems with the MR

• The MR is filled in as requested (including labels, milestones, and reviewers)

• The documentation is up-to-date

• All nullable parameters are marked as such

core/src/main/java/nl/tudelft/ewi/auta/core/controller/SubmissionController.java

@@ -245,12 +245,12 @@ public class SubmissionController extends ControllerBase {
         res.put("aid", submission.getAssignmentId());
         res.put("name", submission.getName());
 
-        final var resultsOptional = entityRepository.findById(sid);
-        res.put("results", resultsOptional.orElse(null));
+        final var entityContainerOptional = entityRepository.findByParentIds(sid, aid);
+        res.put("results", entityContainerOptional.map(EntityContainer::getEntity).orElse(null));
 
         if (format.isPresent() && format.get().equalsIgnoreCase("html")) {
             res.put("report",
-                    resultsOptional
+                    entityContainerOptional
                             .map(EntityContainer::getEntity)
                             .map(this.htmlReportGenerator::generate)
                             .orElse(null)