Specify the user model using the AUTH_USER_MODEL setting

Specify the user model using the AUTH_USER_MODEL setting as discussed in the Docs.
https://docs.djangoproject.com/en/dev/topics/auth/customizing/#referencing-the-user-model

app/models/plugin_datum.py

@@ -1,13 +1,13 @@
 import logging
 from django.db import models
 from django.contrib.postgres import fields
-from django.contrib.auth.models import User
+from django.conf import settings
 
 logger = logging.getLogger('app.logger')
 
 class PluginDatum(models.Model):
     key = models.CharField(max_length=255, help_text="Setting key", db_index=True)
-    user = models.ForeignKey(User, null=True, default=None, on_delete=models.CASCADE, help_text="The user this setting belongs to. If NULL, the setting is global.")
+    user = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, default=None, on_delete=models.CASCADE, help_text="The user this setting belongs to. If NULL, the setting is global.")
     int_value = models.IntegerField(blank=True, null=True, default=None, help_text="Integer value")
     float_value = models.FloatField(blank=True, null=True, default=None, help_text="Float value")
     bool_value = models.NullBooleanField(blank=True, null=True, default=None, help_text="Bool value")