Allow genres from the GND and show it as facets
Similary to how we allow BK, we should be able to allow genres from the GND and show it as a facet. Here is a list to the GND genres: https://explore.gnd.network/search?f.gnd_systematik=12.3&f.satzart=Sachbegriff&rows=25
<subject>
<id type="https://explore.gnd.network/gnd/">4051288-5</id>
<value>Sage</value>
</subject>
<subject>
<id type="https://explore.gnd.network/gnd/">4044843-5</id>
<value>Chorlied</value>
</subject>
Because we could use the GND for many things (people, places, topics, genres), I think it could be a good idea to specify for what exactly we are using the GND so that it shows as the name of the category of the genres. Perhaps other options are possible, like adding several genre elements and linking them to the GND (probably the schema does not allow this).
We should talk with MET and perhaps with people from the GND-DNB about this.