feat(apps/submissions): creat folder submissions and initial model

apps/submissions/models.py

@@ -0,0 +1,19 @@
+from django.db.models import CASCADE, ForeignKey, TextField
+
+from apps.tasks.models import Task
+from apps.users.models import User
+from core.models import TimestampedModel
+
+
+class Submission(TimestampedModel):
+    id: int
+
+    author = ForeignKey(User, related_name="submissions", on_delete=CASCADE)
+    task = ForeignKey(Task, related_name="submissions", on_delete=CASCADE)
+    code = TextField()
+
+    class Meta:
+        db_table = "submissions"
+
+    def __str__(self) -> str:
+        return f"{self.code} #{self.id}"