Follow-up from Factory mvp's - Check / Update Factory for consistency in file writing procedure i.e use of pad_timeseries.

The following discussion from !380 (merged) should be addressed:

• @erigler started a discussion: (+1 comment)

  Re. # All traces should have the same starttime and delta per convention:

  This is not necessarily true. That said, I'm not sure what is best here; it may be as basic as using geomagio.TimeseriesUtilty.pad_timeseries().

  We may also want to look at this question across the various geomag-algorithms factories, and try to make them as consistent as possible (a different MR of course)