Adds option to support direct uploads (#14)

* Adds option to support direct uploads

* Adds documentation for direct_upload option

README.md

@@ -87,6 +87,20 @@ class ModelDashboard < Administrate::BaseDashboard
 end
 ```
 
+### direct_upload
+If you want to upload directly from the browser to the cloud you can use direct_upload
+```ruby
+class ModelDashboard < Administrate::BaseDashboard
+  ATTRIBUTE_TYPES = {
+    attachments: Field::ActiveStorage.with_options({direct_upload: true}),
+    # ...
+  }
+  # ...
+end
+```
+
+Don't forget to include [ActiveStorage JavaScript](https://edgeguides.rubyonrails.org/active_storage_overview.html#direct-uploads). You can use `rails generate administrate:assets:javascripts` to be able to customize Administrate JavaScripts in your application.
+
 ## Things To Do:
 - [x] upload single file
 - [x] adding image support through url_for to support 3rd party cloud storage

app/views/fields/active_storage/_form.html.erb

@@ -26,5 +26,5 @@ By default, the input is a text field for the image's URL.
     Add:
   <% end %>
 
-  <%= f.file_field field.attribute, multiple: field.many? %>
+  <%= f.file_field field.attribute, multiple: field.many?, direct_upload: field.direct? %>
 </div>

lib/administrate/field/active_storage.rb

@@ -20,6 +20,10 @@ def many?
         data.class.name == "ActiveStorage::Attached::Many"
       end
 
+      def direct?
+        options.fetch(:direct_upload, false)
+      end
+
       # def destroy_path?
       #   options.fetch(:destroy_path, false).present?
       # end