code: public static String getUserAgent() {
          if (USER_AGENT == null) {
              USER_AGENT = String.format(Locale.ENGLISH, "%s/%s (%s/%s)",
                      PRODUCT_NAME,
                      Version.SYNC_PROTOCOL_VERSION,
                      Version.getVersionName(),
                      Version.getCommitHash());
          }
          return USER_AGENT;
      }
docs: Return User-Agent value
  Format: ex: CouchbaseLite/1.2 (Java Linux/MIPS 1.2.1/3382EFA)