docs: public static @Nonnull ConfidentialStore get() {
          if (TEST!=null) return TEST.get();
  
          Jenkins j = Jenkins.getInstance();
          Lookup lookup = j.lookup;
          ConfidentialStore cs = lookup.get(ConfidentialStore.class);
          if (cs==null) {
              try {
                  Iterator<ConfidentialStore> it = ServiceLoader.load(ConfidentialStore.class, ConfidentialStore.class.getClassLoader()).iterator();
                  if (it.hasNext()) {
                      cs = it.next();
                  }
              } catch (ServiceConfigurationError e) {
                  LOGGER.log(Level.WARNING, "Failed to list up ConfidentialStore implementations",e);
                  // fall through
              }
  
              if (cs==null)
                  try {
                      cs = new DefaultConfidentialStore();
                  } catch (Exception e) {
                      // if it's still null, bail out
                      throw new Error(e);
                  }
  
              cs = lookup.setIfNull(ConfidentialStore.class,cs);
          }
          return cs;
      }