changed the interface of on_primary_key to have a third parameter of type primary_key_attribute

include/matador/utils/field_attributes.hpp

@@ -9,10 +9,10 @@ namespace matador::utils {
 
 /**
  * This class represents field attributes in
- * form of size and constraints for a database
+ * the form of size and constraints for a database
  * field (column)
  *
- * Currently the size is only applied
+ * Currently, the size is only applied
  * to a field of type string leading
  * to VARCHAR(size).
  */