Add support for additional ACL actions
Opencast supports to ACL actions out-of-the-box: read and write.
The goal of this task is to enhance the ACL editor of the admin-ui to allow users the make use of other ACLs actions.
The set of additional ACL actions (in means of additional to the standard Opencast ACL actions) can be configured in a configuration file.
This allows users to set ACL actions relevant for third-party applications without interfering with the standard Opencast ACL actions.
At SWITCH, for example, we use those additional ACL actions to set permissions for a given event that are only relevant for our proprietary video portal. Example: We have an "download" action that controls whether a user is allowed to download content on our video portal.
Note that additional ACL actions have no meaning to Opencast itself - it just forwards them to publications channels that can use those additional information for whatever they want.