Policy groups allow you to group policies by shared conditions.
This can help simplify the mental overhead of large sets of policies.
For example:
```elixir
policies do
policy_group actor_attribute_equals(:role, :owner) do
policy action_type(:read) do
authorize_if expr(owner_id == ^actor(:id))
end
policy action_type([:create, :update, :destroy]) do
forbid_if
authorize_if expr(owner_id == ^actor(:id))
end
end
end
```
