code: public static Query withMatchingString(String field, String value, boolean caseInsensitive) {
          return caseInsensitive ? regex(field, escapeRegExPattern(value), caseInsensitive, false, false, false) : withValue(field, eq, value);
      }
docs: <pre>
  { field: <field>, regex: <pattern>, caseInsensitive: <caseInsensitive>, ... }
  </pre>