- The `agreement` model now features mail and activities from its base module.
- The `agreement_legal` module doesn't need to add mail support now.
- Add activities to form views.
@Tecnativa TT22477
we move the is_template field definition and the agreement.type model from
the agreement_legal module to the agreement module.
The fields are not displayed by default, unless the feature is enabled through a
technical feature group, this is configurable in the agreement_sale module (because agreement
in itself has no UI, and agreement_legal enables the feature by default)
