[Sharing NG] Add a sharing NG equivalent for the `default_permissions` capability

[JammingBen]

Describe the bug

Currently, the capabilities contain default_permissions inside the files_sharing object to determine the default permissions a link should have upon creating. This permission concept is however deprecated and originates from the old OCS API. Hence we need a new sharing NG equivalent, I guess default_type, since this property now determines the permissions of a link.

Steps to reproduce

1. Check default_permissions inside the capabilities response of the server: https://host.docker.internal:9200/ocs/v1.php/cloud/capabilities

Expected behavior

There is some NG equivalent for the default_permissions (e.g. default_type).

Actual behavior

We only have default_permissions.

cc @rhafer

[JammingBen]

@micbar You know my gripes with the link type property, but I guess we will be stuck with it for at least the near future, right?

So I see 2 possible options to solve this issue:

• Introduce default_type to the capabilities. Possible values are all supported link types.
• Introduce default_type_internal to the capabilities. Possible values are true or false. This would be a little more restrictive as users can only determine of links will be created with the internal or the view type.

Also, how do you handle deprecated capabilities and env vars in oCIS? Just remove them, or announce the deprecation somewhere?