fix: don't use :"timestamptz(6)" in ecto storage type

Author: zachdaniel

lib/migration_generator/migration_generator.ex

@@ -3364,8 +3364,13 @@ defmodule AshPostgres.MigrationGenerator do
 
   defp migration_type(other, constraints) do
     type = Ash.Type.get_type(other)
+    Code.ensure_loaded(type)
 
-    migration_type_from_storage_type(Ash.Type.storage_type(type, constraints))
+    if function_exported?(type, :migration_type, 1) do
+      type.migration_type(constraints)
+    else
+      migration_type_from_storage_type(Ash.Type.storage_type(type, constraints))
+    end
   end
 
   defp migration_type_from_storage_type(:string), do: :text

lib/type.ex

@@ -11,8 +11,11 @@ defmodule AshPostgres.Type do
   @callback postgres_reference_expr(Ash.Type.t(), Ash.Type.constraints(), term) ::
               {:ok, term} | :error
 
+  @callback migration_type(Ash.Type.constraints()) :: term()
+
   @optional_callbacks value_to_postgres_default: 3,
-                      postgres_reference_expr: 3
+                      postgres_reference_expr: 3,
+                      migration_type: 1
 
   defmacro __using__(_) do
     quote do

lib/types/timestamptz.ex

@@ -28,10 +28,6 @@ defmodule AshPostgres.Timestamptz do
   attribute :timestamp, :timestamptz
   timestamps type: :timestamptz
   ```
-
-      
-
-
   """
   use Ash.Type.NewType, subtype_of: :datetime, constraints: [precision: :second]
 

lib/types/timestamptz_usec.ex

@@ -21,14 +21,16 @@ defmodule AshPostgres.TimestamptzUsec do
   timestamps type: :timestamptz_usec
   ```
 
-      
-
   Please see `AshPostgres.Timestamptz` for details about the usecase for this type.
   """
   use Ash.Type.NewType, subtype_of: :datetime, constraints: [precision: :microsecond]
 
   @impl true
   def storage_type(_constraints) do
+    :timestamptz
+  end
+
+  def migration_type(_constraints) do
     :"timestamptz(6)"
   end
 end