Automations: Combined Add + Same As operation for compatible fields

Automations currently support modifying multi-item fields with the "Same as" operator, and the "Add" operator.

The "Same as" operator is useful for greatly reducing the number of automations required when mapping field values, but the downside is that it overwrites the target field with a single value.

The "Add" operator allows values to be added to the target field iteratively, but requires a specific value to be specified per rule, so the downside is that an individual rule is required for every value you want to add.

An operator which combines the Add + Same As functionality would be very useful for anyone who wants to use the Add operation dynamically, in a single rule, such as to better capture historical values of a field which is subject to change, in a manner which is easily visible and reportable.

For example, our own specific use case is we want to capture a list of all users who have been assigned to an item, past or present. This is visible in Aha via the item's history, but it is often difficult to find, and it's not reportable.

Suggested functionality would be: in rules where the "Same as" and "Add" operations are currently both supported, a new "Add the same as" operator would also be available, which combines the functionality of the 2 operations.