When you use a composite field (two text fields for example) in a dialog of a component of a page, the field doesn't appear in the exported file of the page using the content translation module.

Steps to reproduce:

1. Configure a dialog with a composite field and i18n enabled. Example attached.
2. Use this dialog in a component inside a page with at least 2 languages configured.
3. Export the page for translation using the content translation app (xls or csv).
4. Open the exported file.

Result:
The file doesn't contain any rows for the field filled.

Expected result:
The file contains a row for each subfield (i18n enabled) of the composite field.

Note: The type info.magnolia.ui.form.field.definition.CompositeFieldDefinition was registered as control type to export.

This issue has been tested with textfields and/or select fields inside a composite field with either both i18n enabled or only one.

This issue has been tested with CompositeTransformer and DelegatingCompositeFieldTransformer.