[#133] Fix that we were trying use regex to match ID as single digit …

…and this did not work for more than 10 files in id

README.md

@@ -287,7 +287,7 @@ The helper is detecting the value of the `multiple` property based on the mount
 ### File and Group wrappers
 
 When you mount either Uploadcare File or Group to an attribute, this attribute is getting wrapped with
-a Uploadcare object. This feature adds some usefull methods to the attribute.
+a Uploadcare object. This feature adds some useful methods to the attribute.
 
 #### Uploadcare File
 
@@ -300,7 +300,7 @@ class Post < ApplicationRecord
 end
 ```
 
-And then you create a new Post object specifying a CDN-url for your prevously uploaded Uploadcare file:
+And then you create a new Post object specifying a CDN-url for your previously uploaded Uploadcare file:
 
 ```console
 $ post = Post.create(picture: "https://ucarecdn.com/2d33999d-c74a-4ff9-99ea-abc23496b052/")

lib/uploadcare/rails/active_record/mount_uploadcare_file_group.rb

@@ -13,7 +13,7 @@ module ActiveRecord
       module MountUploadcareFileGroup
         extend ActiveSupport::Concern
 
-        GROUP_ID_REGEX = /\b[0-9a-f]{8}\b-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-\b[0-9a-f]{12}\b~\d/.freeze
+        GROUP_ID_REGEX = /\b[0-9a-f]{8}\b-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-\b[0-9a-f]{12}\b~\d+/.freeze
 
         def build_uploadcare_file_group(attribute)
           cdn_url = attributes[attribute.to_s].to_s