Fixed #12030 -- Validate integer field range at the model level.

Thanks to @timgraham for the review.

tests/model_fields/models.py

@@ -55,11 +55,27 @@ class BigS(models.Model):
     s = models.SlugField(max_length=255)
 
 
-class BigInt(models.Model):
+class SmallIntegerModel(models.Model):
+    value = models.SmallIntegerField()
+
+
+class IntegerModel(models.Model):
+    value = models.IntegerField()
+
+
+class BigIntegerModel(models.Model):
     value = models.BigIntegerField()
     null_value = models.BigIntegerField(null=True, blank=True)
 
 
+class PositiveSmallIntegerModel(models.Model):
+    value = models.PositiveSmallIntegerField()
+
+
+class PositiveIntegerModel(models.Model):
+    value = models.PositiveIntegerField()
+
+
 class Post(models.Model):
     title = models.CharField(max_length=100)
     body = models.TextField()