[IMP] web: make it possible to add classes to fields

`additionalClasses` can now be set on field components to add certain
classes the wrapper should have.
This is useful in case css rules have been defined on a field widget
that we want to inherit from.

X-original-commit: e882c892ad2bf476a6d25cbd90e72974c5453a38
Part-of: odoo/odoo#100764

addons/web/static/src/views/fields/field.js

@@ -99,6 +99,11 @@ export class Field extends Component {
             [`o_field_${this.type}`]: true,
             [_class]: Boolean(_class),
         };
+        if (this.FieldComponent.additionalClasses) {
+            for (const cls of this.FieldComponent.additionalClasses) {
+                classNames[cls] = true;
+            }
+        }
 
         // generate field decorations classNames (only if field-specific decorations
         // have been defined in an attribute, e.g. decoration-danger="other_field = 5")