Add models for graph app

graph/models.py

@@ -1,3 +1,32 @@
 from django.db import models
 
-# Create your models here.
+from market.models import Product
+
+
+class Transaction(models.Model):
+    product = models.ForeignKey(
+        Product, on_delete=models.CASCADE, related_name="transactions"
+    )
+    price = models.IntegerField()
+    created_at = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        ordering = ["-created_at"]
+
+    def __str__(self):
+        return f"{self.product} : {self.price}"
+
+
+class MonthlyTransaction(models.Model):
+    product = models.ForeignKey(
+        Product, on_delete=models.CASCADE, related_name="monthly_transactions"
+    )
+    year = models.IntegerField()
+    month = models.IntegerField()
+    price = models.IntegerField()
+
+    class Meta:
+        ordering = ["-year", "-month"]
+
+    def __str__(self):
+        return f"{self.product} : {self.year}-{self.month}"