protected void setProvider(String name, DiscoItemsProvider provider) {
        entities.put(name, provider);
    }
Sets that a given DiscoItemsProvider will provide the items related to a given entity. This
message must be used when new modules (e.g. MUC) are implemented and need to provide
the items related to them.

@param name     the name of the entity.
@param provider the DiscoItemsProvider that will provide the entity's items.
xmppserver/src/main/java/org/jivesoftware/openfire/disco/IQDiscoItemsHandler.java