Expected column mrn does not exist and fails for samples run via redcap lambda payload

[alexiswl]

Expected column mrn but did not find it in columns disease_id, requesting_physicians_first_name, requesting_physicians_last_name, subject_id, library_id, date_collected, date_received, patient_urn, sample_type, disease_name, gender, pierian_metadata_complete, project_name, external_specimen_id, external_subject_id, panel_type, is_identified, specimen_type, indication, hospital_number, accession_number, date_accessioned

[alexiswl]

Check is done before external subject id is renamed to mrn, however now that we support deidentified specimens through the clinical pipeline, we can instead just replace mrn with external_subject_id instead since external_subject_id is also required for deidentified samples and is renamed to study_subject_identifier.