Clarify object validation operators in documentation for self-service experiences

Author: kodjomiles

docs/actions-and-automations/create-self-service-experiences/setup-ui-for-action/user-inputs/object.md

@@ -153,8 +153,8 @@ resource "port_action" "myAction" {
 
 Object validations support the following operators:
 
-- `properties` - which keys must appear and what their type should be;
-- `additionalProperties` - are keys not defined in `properties` allowed and what their type should be;
+- `properties` - defines the type for keys if they appear (use `required` array to make keys mandatory);
+- `additionalProperties` - whether keys not defined in `properties` are allowed (boolean) or what type they should be (type definition);
 - `patternProperties` - which regex pattern should properties follow
 
 :::tip