Fix CondClauseError when using use_parent_field_for_type with matching

types

When using `use_parent_field_for_type` option in `polymorphic_embeds_one`,
the `action_and_struct/4` function's cond block was missing a clause to
handle the case when both `type_from_parent_field` and `type_from_map`
are present and match.

The existing cond only handled:
1. type_from_parent_field is nil -> :type_not_found
2. type_from_map is nil -> get module and return action/struct
3. types don't match -> raise error

This caused a CondClauseError when form params included the `__type__`
field matching the parent field type (e.g., during form validation).

Added a `true` clause to handle the matching types case, which behaves
the same as when type_from_map is nil - it uses the parent field type
to determine the module and returns the appropriate action/struct tuple.

Author: zacksiri

lib/polymorphic_embed.ex

@@ -360,6 +360,16 @@ defmodule PolymorphicEmbed do
 
         to_string(type_from_parent_field) != to_string(type_from_map) ->
           raise "type specified in the parent field \"#{type_from_parent_field}\" does not match the type in the embedded map \"#{type_from_map}\""
+
+        true ->
+          # type_from_parent_field and type_from_map match
+          module = get_polymorphic_module_for_type(type_from_parent_field, types_metadata)
+
+          if is_nil(data_for_field) or data_for_field.__struct__ != module do
+            {:insert, struct(module)}
+          else
+            {:update, data_for_field}
+          end
       end
     else
       case get_polymorphic_module_from_map(params, type_field_name, types_metadata) do