API uploads images via URL

This enhancement give the images API the ability to create images from URLs.  A
simple check determines whether or not the attachment parameter is a URL.

If it is a URL: OpenURI is used to download the image and it subsequently
undergoes the standard post upload processing (via paperclip).  After
processing the image, the other attributes (besides :attachment) are updated on
the resultant Spree::Image.

If it is not a URL: the attachment parameter is handled in the same manner
it was prior to this commit.

API documentation added.

Uses static image from solidus repo, to avoid external dependency

api/app/controllers/spree/api/images_controller.rb

@@ -15,7 +15,11 @@ def show
 
       def create
         authorize! :create, Image
-        @image = scope.images.create(image_params)
+
+        @image = scope.images.build(image_params.except(:attachment))
+        @image.attachment = prepared_attachment
+        @image.save
+
         respond_with(@image, status: 201, default_template: :show)
       end
 
@@ -44,6 +48,17 @@ def scope
           Spree::Variant.find(params[:variant_id])
         end
       end
+
+      def prepared_attachment
+        uri = URI.parse image_params[:attachment]
+        if uri.is_a? URI::HTTP
+          URI.open(image_params[:attachment])
+        else
+          image_params[:attachment]
+        end
+      rescue URI::InvalidURIError
+        image_params[:attachment]
+      end
     end
   end
 end

api/openapi/api.oas2.yml

@@ -5885,6 +5885,7 @@ definitions:
         type: string
       attachment:
         type: string
+        description: 'This field can be used to pass an image URL. When used in this manner, the image undergoes the standard post upload processing via paperclip.'
       position:
         type: integer
       viewable_type:

api/spec/requests/spree/api/images_controller_spec.rb

@@ -32,6 +32,22 @@ module Spree
         end.to change(Image, :count).by(1)
       end
 
+      it 'can upload a new image from a valid URL' do
+        expect do
+          post spree.api_product_images_path(product.id), params: {
+            image: {
+              attachment: 'https://github.com/solidusio/brand/raw/1827e7afb7ebcf5a1fc9cf7bf6cf9d277183ef11/PNG/solidus-logo-dark.png',
+              viewable_type: 'Spree::Variant',
+              viewable_id: product.master.to_param,
+              alt: 'just a test'
+            },
+          }
+          expect(response.status).to eq(201)
+          expect(json_response).to have_attributes(attributes)
+          expect(json_response[:alt]).to eq('just a test')
+        end.to change(Image, :count).by(1)
+      end
+
       context "working with an existing product image" do
         let!(:product_image) { product.master.images.create!(attachment: image('thinking-cat.jpg')) }