Support KorapSRU to provide access to protected VC #803
Description
KorAP should support searching in protected virtual corpora for the Text+ project via CLARIN FCS. KorapSRU is the FCS endpoint that currently enable access to free resources only in DeReKo.
To access protected resources, authentication and authorization is inevitable. However, Kustvakt provides search on public metadata of all resources, that can be used to inform the number of results. KorAPSRU should use this service for search on protected resources.
To achieve this, some implementations are needed as described in the sub-tasks.