Allow to specify an counter-item in list-type options

Current Behavior

There are several list-type options, like ignored_prefixes, ignored_suffixes or the new disallowed_types_for_dt (NXDRIVE-2311).

For all list-type options, when they are defined server-side and client-side, a concatenation is done with all deduplicated items.

Possible Issue

Let's choose the disallowed_types_for_dt option, others are not interesting for our purpose (even if they will benefit of the possible improvement). That option contains document types where Direct Transfer is not allowed and is set to ["Domain", "Section"] by default.

And let's say a customer allowed Direct Transfer into Section, then it will never be possible client-side.

Proposed Enhancement

The proposal is to allow a specific syntax for such options that will invalidate the item from the list. To be more precise, if one wants to remove the item Section from the option, it will set the item to !Section.

Example of the server-side configuration:

{
  "disallowed_types_for_dt": ["!Section", "CustomFolder"]
}

And consider the client-side default value:

disallowed_types_for_dt = ("Domain", "Section")

Then, the application will have the following concatenated list:

- CustomFolder
- Domain
- Section
- !Section

And it will automatically filter out items starting with a !, resulting with the following final list:

- CustomFolder
- Domain

Note that if the item is not part of the list, the counter-item will be a no-op.