Prevent validation of fields when uploading a file through a hippo:resource field

Uploading a file via a hippo:resource field triggers the field validation process of other fields.

Reproduction path:

• Create a document type with a couple of primitive fields such as a String and mark these fields as required
• Add a hippo:resource field to this document type.
• Click on 'Done' and 'Commit' to finalize creation of document type
• Create a new document of this document type and keep the primitive fields empty
• Upload a file using the hippo:resource field.

Expected result: The file is uploaded, the hippo:resource field is validated and no validation is performed on the other fields
Actual result: The file is uploaded and validation is performed on the document as a whole and all other fields are also validated indicating that the required fields are empty.