Function parameterized_create_for_relationship 

pub fn parameterized_create_for_relationship(
    rel_type: &str,
    start_label: &str,
    start_column: &str,
    start_match_property: &str,
    end_label: &str,
    end_column: &str,
    end_match_property: &str,
    properties: &[ColumnSpec],
) -> Result<String, String>

Build the Cypher template for a relationship mapping.