permission set names should be constants on the domain class

atst/models/portfolio.py

@@ -4,6 +4,7 @@ from itertools import chain
 
 from atst.models import Base, mixins, types
 from atst.models.portfolio_role import PortfolioRole, Status as PortfolioRoleStatus
+from atst.domain.permission_sets import PermissionSets
 from atst.utils import first_or_none
 from atst.database import db
 
@@ -23,7 +24,7 @@ class Portfolio(Base, mixins.TimestampsMixin, mixins.AuditableMixin):
     @property
     def owner(self):
         def _is_portfolio_owner(portfolio_role):
-            return "portfolio_poc" in [
+            return PermissionSets.PORTFOLIO_POC in [
                 perms_set.name for perms_set in portfolio_role.permission_sets
             ]