Enhance fields conditional logic

[jbarbosa13]

At the moment, we are able to hide or show a certain field using conditional logic. We can't, however, change other admin properties conditionally.

Scenario:
A very useful scenario is changing the readOnly property conditionally. There are multiple questions about this in Discord (like this).

Example: I have a checkbox field and a text field. I only want the text field to be editable if the checkbox is active.

Proposal:
Instead of just looking at the visibility of the fields (or just adding the feature to readOnly field), we could make the condition attribute even more generic to change conditionally any type of admin field.

Option 1:
Keep the "global" condition, but return an object.

  admin: {
    condition: (data, siblingData, { blockData, path, user }) => {
      if (data.enableGreeting) {
        return { readOnly: false, description: 'Write your greeting here!' }
      } else {
        return { readOnly: true, description: '' }
      }
    },
  },
}

Option 2:
Make it field-by-field based.

We could use, as we do now:

  admin: {
    readOnly: true
  },
}

Or add a function to determine its value:

  admin: {
    readOnly: (data, siblingData, { blockData, path, user }) => { ... }
  },
}