public static <T> ToString<T> joining(
            ToString<T> first,
            ToString<T> second) {
        return joining("", first, second);
    }
Returns an expression that represents the result of the two specified
expressions joined together, forming a single string.

@param first   the first expression
@param second  the second expression
@param <T>     the input entity type
@return        the joined expression
runtime-parent/runtime-compute/src/main/java/com/speedment/runtime/compute/expression/Expressions.java