Validate a field has at least 1 value assigned to it in governed header section

[AleJo2995]

Describe the bug

While performing trestle validations to a governed header instance against its template, there is a validation outperforming the actual expected result of at least having 1 value per field in the instance according to the template. Meaning that if there´s a field without any value on it, the validation is still passing and no errors are being thrown after alll.

To Reproduce

Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior

After performing a header validation against its template, Trestle should log an error for the fields that at least don´t have a value in it.

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Environment

• OS: [e.g. iOS]
• Python version:
• Installed packages: