decap-cms: Cloudinary per field configuration doesn't work

Hi!

Describe the bug I’m using Cloudinary as my media library. I want to set output_filename_only: false for all fields globally and enable it on specific fields but it only works globally.

With the config below I always get the full url.

Expected behavior I would expect to define a global value for how the output of files should look like and change it on specific fields. At least thats how I understand the documentation.

The Cloudinary media library integration can be configured in two ways: globally and per field https://www.netlifycms.org/docs/cloudinary/#cloudinary-configuration-options

In my example I’d expect a full url in the body field and only the file name in the image field

Applicable Versions:

• Netlify CMS version: netlify-cms 2.3.3
• Git provider:GitHub
• OS: macOS High Sierra
• Browser version Firefox Nightlx

CMS configuration

media_library:
  name: cloudinary
  output_filename_only: false
  config:
    cloud_name: my_name
    api_key: 1234567890

collections:
  - name: 'til' 
    label: 'TIL' 
    folder: 'til' 
    create: true
    slug: '{{slug}}' 
    fields:
      - { label: 'Body', name: 'body', widget: 'markdown', required: false }
      - { label: 'Image', name: 'image', widget: 'image', required: false, media_library: { output_filename_only: true }  }

Thank you!