improvement: allow policy conditions to be applied inside their block

```elixir
policy do
  condition [...]
  authorize_if ...
end
```

lib/ash/policy/authorizer/authorizer.ex

@@ -178,7 +178,7 @@ defmodule Ash.Policy.Authorizer do
         """
       ]
     ],
-    args: [:condition],
+    args: [{:optional, :condition}],
     target: Ash.Policy.Policy,
     no_depend_modules: [:condition],
     transform: {Ash.Policy.Policy, :transform, []},
@@ -274,7 +274,7 @@ defmodule Ash.Policy.Authorizer do
           "A check or list of checks that must be true in order for this field policy to apply. If not specified, it always applies."
       ]
     ],
-    args: [:fields, {:optional, :condition, {Ash.Policy.Check.Static, result: true}}],
+    args: [:fields, {:optional, :condition}],
     target: Ash.Policy.FieldPolicy,
     transform: {Ash.Policy.FieldPolicy, :transform, []},
     entities: [

lib/ash/policy/field_policy.ex

@@ -16,11 +16,18 @@ defmodule Ash.Policy.FieldPolicy do
     if Enum.empty?(field_policy.policies) do
       {:error, "Field policies must have at least one check."}
     else
+      field_policy =
+        if field_policy.condition in [nil, []] do
+          %{field_policy | condition: [{Ash.Policy.Check.Static, result: true}]}
+        else
+          field_policy
+        end
+
       {:ok,
        %{
          field_policy
          | policies: Enum.map(field_policy.policies, &set_field_policy_opt/1),
-           condition: Enum.map(List.wrap(field_policy.condition || []), &set_field_policy_opt/1)
+           condition: Enum.map(List.wrap(field_policy.condition), &set_field_policy_opt/1)
        }}
     end
   end

lib/ash/policy/policy.ex

@@ -54,10 +54,14 @@ defmodule Ash.Policy.Policy do
   def transform(policy) do
     if Enum.empty?(policy.policies) do
       {:error, "Policies must have at least one check."}
+    else
+      if policy.condition in [nil, []] do
+        {:ok, %{policy | condition: [{Ash.Policy.Check.Static, result: true}]}}
       else
         {:ok, policy}
       end
     end
+  end
 
   defp build_requirements_expression(policies, authorizer) do
     {at_least_one_policy_expression, authorizer} =

test/actions/aggregate_test.exs

@@ -45,7 +45,8 @@ defmodule Ash.Test.Actions.AggregateTest do
     end
 
     policies do
-      policy always() do
+      policy do
+        condition(always())
         authorize_if expr(public == true)
       end
     end