Make parent resource not mandatory

[gciotola]

What I did

Since we noticed that the app is used mostly to update existing resources, instead of creating new ones, we decided to set the parent resource field as optional.

How to test

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests).
• Make sure to add/update documentation regarding your changes.
• You are NOT deprecating/removing a feature.