Summary

• refactored dav calendar export to use export service to prevent memory exhaustion
• refactored dav calendar export to calendar add meta data to archive
• refactored dav calendar import to use import service to prevent memory exhaustion
• refactored dav calendar import to use calendar meta data from archive
• made import backwards compatible to import version 1 archives.

Checklist

• Code isproperly formatted
• Sign-off message is added to all commits
• Tests (unit,integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement,3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x forstable32)