Checks the format of the Metadata Control Number and warns the user if
the provided value might not adhere to the expected format. check_mcn
has no access to EPHT systems or APIs and cannot check your mcn against
any kind of list of accepted values. It checks if the value is a string,
the length of the string and the pattern and nothing else.
See also
Other checks:
check_content_group_id(),
check_data(),
check_data_content(),
check_jurisdiction_code(),
check_state_fips_code(),
check_submission(),
check_submitter_email(),
check_submitter_name(),
check_submitter_title()