add message and comment

comment/models.py

@@ -0,0 +1,47 @@
+from django.db import models
+
+from account.models import User
+from problem.models import Problem
+from submission.models import Submission
+
+
+class Languages(models.TextChoices):
+    Python = "Python", "Python"
+    C = "C", "C"
+    Cpp = "C++", "C++"
+    Java = "Java", "Java"
+
+
+class Comment(models.Model):
+    problem = models.ForeignKey(Problem, on_delete=models.CASCADE)
+    user = models.ForeignKey(User, on_delete=models.CASCADE)
+    submission = models.ForeignKey(Submission, null=True, blank=True, on_delete=models.SET_NULL)
+    problem_solved = models.BooleanField()
+    language = models.CharField(
+        max_length=10,
+        choices=Languages.choices,
+        null=True,
+        blank=True,
+        verbose_name="解决这道题使用的语言",
+    )
+    description_rating = models.PositiveSmallIntegerField(
+        default=5,
+        verbose_name="题目描述的分数",
+    )
+    difficulty_rating = models.PositiveSmallIntegerField(
+        default=5,
+        verbose_name="题目难度的分数",
+    )
+    comprehensive_rating = models.PositiveSmallIntegerField(
+        default=5,
+        verbose_name="综合的分数",
+    )
+    content = models.TextField(null=True, blank=True)
+    visible = models.BooleanField(default=True)
+    create_time = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        db_table = "comment"
+        ordering = ("create_time",)
+
+