feat: Add Schema#add_serializer to easily update serializer

lib/typed/schema.rb

@@ -27,5 +27,19 @@ def from_hash(hash)
     def from_json(json)
       Typed::JSONSerializer.new(schema: self).deserialize(json)
     end
+
+    sig { params(field_name: Symbol, serializer: Field::InlineSerializer).returns(Schema) }
+    def add_serializer(field_name, serializer)
+      self.class.new(
+        target: target,
+        fields: fields.map do |field|
+          if field.name == field_name
+            Field.new(name: field.name, type: field.type, required: field.required, inline_serializer: serializer)
+          else
+            field
+          end
+        end
+      )
+    end
   end
 end

test/typed/schema_test.rb

@@ -30,4 +30,16 @@ def test_from_json_creates_struct
     assert_success(result)
     assert_payload(MAX_PERSON, result)
   end
+
+  def test_add_serializer_when_no_matching_field_returns_same_schema
+    schema = @schema.add_serializer(:not_here, ->(value) { value + "a" })
+
+    assert_equal(@schema, schema)
+  end
+
+  def test_add_serializer_when_matching_field_returns_schema_with_serializer
+    schema = @schema.add_serializer(:name, ->(value) { value + "a" })
+
+    refute_equal(@schema, schema)
+  end
 end