refactor(src/projects): cache role names in role_display_name

Prevent repeated DB hits by caching Role objects and names.

src/projects/models.py

@@ -116,9 +116,10 @@ class BoardRolePermission(models.Model):
 
     @property
     def role_display_name(self):
+        if not hasattr(BoardRolePermission, "_role_names"):
             from src.accounts.models import Role
 
-        try:
+            BoardRolePermission._role_names = {
-            return Role.objects.get(slug=self.role).name
+                r.slug: r.name for r in Role.objects.only("slug", "name")
-        except Role.DoesNotExist:
+            }
-            return self.role
+        return BoardRolePermission._role_names.get(self.role, self.role)