Which options should XML export support?

[mslw]

Export project XML command is an important one, because it can get everything at once for project preservation or migration. To keep things simple for both ourselves and users, I think we do not need to support all the available flags / options. Below I include all the available API options for project XML, our current status, and my thoughts.

Initial command implementation is in #10

@christian-monch I know you looked at XML export more closely, what are your thoughts? Detailed explanations are in REDCap's docs.

We support:

• returnMetadataOnly (api default: false)
  you can get everything including data (default) or everything but data with --metadata-only

• exportSurveyFields (api default: false, our default: true)
  this is about survey ids / timestamps, we include them by default and allow disabling with --no-survey-fields (we did the same override for export-redcap-form); question is should we be consistent with our other command or with the api here?

We do not support, but maybe we should:

• exportFiles (api default: false)
  docs say: "TRUE will cause the XML returned to include all files uploaded for File Upload and Signature fields for all records in the project (...) Setting this option to TRUE can make the export very large and may prevent it from completing if the project contains many files or very large files."

• exportDataAccessGroups (api default: false)
  this is more about user management if I undestand correctly, so probably less important, although it's a matter of a simple boolean so maybe?

We do not support, and I think we don't need to:

• records / fields / events: (api default: all)
  this would be an option to limit the export to lists of given things - but considering that we think of this command as "dump everything" I think this is not very relevant

• filterLogic (api default: none)
  this would be the option to provide an expression to filter based on values - see comment above