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- it doesn't repeat itself so much now
- TODO: navigation_fa_icon helper is still rubish. It will only take
        string 'xlsx' as a parameter or else return nothing. It is simply
        not as it should be

- Default is always author_volunteer, but it can now also be filtered for
  author AOZ or any author

- replaces the two single purpose filters
  - intern_extern_filter_dropdown
  - activeness_filter_dropdown

This and the new use for waive boolean are now all done by this
boolean_toggler_filter_dropdown

- filter internal/external added to the helper
- translation for resigned adapted to Ausgetreten/Archiviert