Use audit log instead

src/registrar/models/user_portfolio_permission.py

@@ -65,16 +65,6 @@ class UserPortfolioPermission(TimeStampedModel):
         help_text="Select one or more additional permissions.",
     )
 
-    # TODO - this needs a small script to update existing values
-    invitation = models.ForeignKey(
-        "registrar.PortfolioInvitation",
-        null=True,
-        blank=True,
-        # We don't want to accidentally delete invitations
-        on_delete=models.PROTECT,
-        related_name="created_user_portfolio_permission",
-    )
-
     def __str__(self):
         readable_roles = []
         if self.roles: