private Query buildTextQuery(final String fieldName, final String expression) {
        // Contains wildcard chars, so use a query string query, which supports these
        return QueryBuilders.queryString(q -> q
                .fields(fieldName)
                .query(expression)
                .analyzeWildcard(true)
        );
    }
Creates an Elasticsearch query for a `keyword` field appropriate for the expression content
stroom-search/stroom-search-elastic/src/main/java/stroom/search/elastic/search/SearchExpressionQueryBuilder.java