Automatically detect person file

[anwarfg]

Is this the right issue type?

• Yes, I'm planning work for this project team.

Summary

The person file argument can be removed (set as an optional arg) and automatically detected since it is defined as the file with the person_id as the first column.

This could be as simple as opening all the input files, reading the header and checking the first entry until we find person_id. It would be more complete if we check all files, as it'd be ambiguous and should throw an error if there are multiple.

Fewer required args make it easier to run.

Acceptance Criteria

• person-file is an optional argument.

• person-file can be detected by checking files in the input dir.

• Tests pass.

• Documentation added.

Confirm creation

• This issue is ready