Fixed missing 'size' and 'type' props on a third-party category images

[vovayatsyuk]

Description

Fixes hardcoded 'image' key when processing ImageBackendModel attribute.

Manual testing scenarios

1. In order to test the issue, you need to create custom ImageBackendModel attribute and add it to the category edit form
2. Upload third-party image (leave the image field empty) and save category
3. Third-party image will not have required 'size' and 'type' properties during page rendering
4. The main image will have 'size' and 'type' properties of third-party image

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[orlangur]

@vovayatsyuk thanks for your contribution!

In order to speed up testing and PR processing, could you please provide code snippet used to create custom image attribute?

[vovayatsyuk]

1. This is a code to create an attribute. You can use it in any action without writing an upgrade:

   $setup = $this->_objectManager->get(\Magento\Framework\Setup\ModuleDataSetupInterface::class);
   $categorySetupFactory = $this->_objectManager->get(\Magento\Catalog\Setup\CategorySetupFactory::class);
   $setup->startSetup();
   $categorySetup = $categorySetupFactory->create(['setup' => $setup]);
   $categorySetup->addAttribute(
       \Magento\Catalog\Model\Category::ENTITY,
       'thumbnail_test',
       [
           'type' => 'varchar',
           'label' => 'Thumbnail test',
           'input' => 'image',
           'backend' => 'Magento\Catalog\Model\Category\Attribute\Backend\Image',
           'required' => false,
           'sort_order' => 4,
           'global' => \Magento\Eav\Model\Entity\Attribute\ScopedAttributeInterface::SCOPE_STORE,
           'group' => 'General Information',
       ]
   );
   $setup->endSetup();

2. Add this code to Magento/Catalog/view/adminhtml/ui_component/category_form.xml above the image field:

   <field name="thumbnail_test" sortOrder="30" formElement="fileUploader">
       <argument name="data" xsi:type="array">
           <item name="config" xsi:type="array">
               <item name="source" xsi:type="string">category</item>
           </item>
       </argument>
       <settings>
           <elementTmpl>ui/form/element/uploader/uploader</elementTmpl>
           <dataType>string</dataType>
           <label translate="true">Category Thumbnail</label>
           <visible>true</visible>
           <required>false</required>
       </settings>
       <formElements>
           <fileUploader>
               <settings>
                   <required>false</required>
                   <uploaderConfig>
                       <param xsi:type="url" name="url" path="catalog/category_image/upload"/>
                   </uploaderConfig>
                   <previewTmpl>Magento_Catalog/image-preview</previewTmpl>
               </settings>
           </fileUploader>
       </formElements>
   </field>

3. Now you will be able to upload thumbnail from the category page, save category, and reproduce the bug:

[orlangur]

Excellent 👍