Sub Form Field Rule Trigger

Must reference the `api_id` of an existing field defined within `form_fields_per_document`. Trigger and action fields and groups must belong to the same signer.

Different field types allow different `operator` values: - Field type of **text**: - **is**: exact match - **not**: not exact match - **match**: regular expression, without /. Example: - OK `[a-zA-Z0-9]` - Not OK `/[a-zA-Z0-9]/` - Field type of **dropdown**: - **is**: exact match, single value - **not**: not exact match, single value - **any**: exact match, array of values. - **none**: not exact match, array of values. - Field type of **checkbox**: - **is**: exact match, single value - **not**: not exact match, single value - Field type of **radio**: - **is**: exact match, single value - **not**: not exact match, single value

**value** or **values** is required, but not both. The value to match against **operator**. - When **operator** is one of the following, **value** must be `String`: - `is` - `not` - `match` Otherwise, - **checkbox**: When **type** of trigger is **checkbox**, **value** must be `0` or `1` - **radio**: When **type** of trigger is **radio**, **value** must be `1`

**values** or **value** is required, but not both. The values to match against **operator** when it is one of the following: - `any` - `none`