static RowMapperFactory of(Type type, RowMapper<?> mapper) {
        return (t, ctx) -> t.equals(type)
                ? Optional.of(mapper)
                : Optional.empty();
    }
Create a RowMapperFactory from a given {@link RowMapper} that matches
a {@link Type} exactly.

@param type the type to match with equals.
@param mapper the mapper to return

@return the factory
core/src/main/java/org/jdbi/v3/core/mapper/RowMapperFactory.java