add did:web config option

[jchartrand]

We need to expose the did:web configuration option on the status service. The underlying credential-status-manager-db does support did:web, it just hasn't yet been exposed on the status service.

This is for the did that is used to sign the status list.

This will be important because the did used to sign the status list must match the did used to sign any VCs for which the status list is used. In other words, the did used with the signing-service must match the did used with the status-service-db, and if the signing-service is using a did:web then so to must the status-service-db.