@Override
    public boolean isReadOnly() {
      return getOrDefault(READONLY_KEY, Boolean::valueOf, DEFAULT_READONLY);
    }
Check if the readOnly flag of the table is set. If the readOnly flag is set then the contents
of the table can only be read from but not modified.
@return true if all columns in the table should be read only
hbase-client/src/main/java/org/apache/hadoop/hbase/client/TableDescriptorBuilder.java