code: public static <TItem> Bson eq(final String fieldName, @Nullable final TItem value) {
          return new SimpleEncodingFilter<TItem>(fieldName, value);
      }
docs: Creates a filter that matches all documents where the value of the field name equals the specified value. Note that this doesn't
  actually generate a $eq operator, as the query language doesn't require it.
  
  @param fieldName the field name
  @param value     the value, which may be null
  @param <TItem>   the value type
  @return the filter
  @mongodb.driver.manual reference/operator/query/eq $eq