Use helper methods for adding and removing permissions

atst/models/role.py

@@ -1,5 +1,6 @@
 from sqlalchemy import String, Column
 from sqlalchemy.dialects.postgresql import ARRAY
+from sqlalchemy.orm.attributes import flag_modified
 
 from atst.models import Base
 from .types import Id
@@ -12,3 +13,15 @@ class Role(Base):
     name = Column(String, index=True, unique=True)
     description = Column(String)
     permissions = Column(ARRAY(String), index=True, server_default="{}")
+
+    def add_permission(self, permission):
+        perms_set = set(self.permissions)
+        perms_set.add(permission)
+        self.permissions = list(perms_set)
+        flag_modified(self, "permissions")
+
+    def remove_permission(self, permission):
+        perms_set = set(self.permissions)
+        perms_set.discard(permission)
+        self.permissions = list(perms_set)
+        flag_modified(self, "permissions")