README.md in materialist-3.7.0 vs README.md in materialist-3.8.0

@@ -153,12 +153,12 @@
 
   sidekiq_options queue: :orderweb_service, retry: false
 
   persist_to :zone
 
-  source_key :source_id do |url|
-    /(\d+)\/?$/.match(url)[1]
+  source_key :source_id do |url, response|
+    /(\d+)\/?$/.match(url)[1] # or response.dig(:some_attr)
   end
 
   capture :id, as: :orderweb_id
   capture :code
   capture :name
@@ -187,13 +187,13 @@
 #### `persist_to <model_name>`
 describes the name of the active record model to be used.
 If missing, materialist skips materialising the resource itself, but will continue
 with any other functionality -- such as `materialize_link`.
 
-#### `source_key <column> <url_parser_block> (default: url)`
+#### `source_key <column> <parser_block> (default: url, resource response body[create, update action only])`
 describes the column used to persist the unique identifier parsed from the url_parser_block.
 By default the column used is `:source_url` and the original `url` is used as the identifier.
-Passing an optional block allows you to extract an identifier from the URL.
+Passing an optional block allows you to extract an identifier from the URL and captured attributes.
 
 #### `capture <key>, as: <column> (default: key)`
 describes mapping a resource key to a database column.
 
 You can optionally provide a block for parsing the value: