String appendOneLevelOfId(String baseIdSegment, String id) {
        if ("".equals(baseIdSegment)) return id.split("/")[0];
        String theRest = id.substring(baseIdSegment.length());
        if ("".equals(theRest)) return id;
        theRest = theRest.replaceFirst("/", "");
        String theRestFirstSeg = theRest.split("/")[0];
        return baseIdSegment+"/"+theRestFirstSeg;
    }
Given baseIdSegment search/ and id search/container/default.0, return search/container
@return id segment with one extra level from the id appended
configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java