Translation losses in Exchange exports

[meain]

Created issues for things that we could fix.

Email (as eml)

• Handle custom attachments in email exports #4772
• In a multiplart email containing HTML and text, only the HTML is exported. We do not have the text data available in backup.
• We don't export certain meta headers like DKIM status, priority, DSN etc. Data is not available in backup, but available if we download MIME.

Contacts (as vcf)

• Backup, restore and export contact photo #5059
• Addresses gets combined into a single string. Spec does not have separate fields.
• Following values are not exported: weddingAnniversary, gender, websites. Available in beta API.

Event (as ics)

• Handling multiple locations in ics #5003
• Addresses gets combined into a single string. Spec does not have separate fields.
• Inline attachments do not show up properly if exported item in imported in Outlook
• Attachment names are lost when exported files are imported to Outlook
• Original timezone is not retained when exporting (everything is converted to UTC)
• Descriptions containing UTF8 strings will look slightly different in exported file. Cannot use the mechanism used for restoring as-is as field does not support UTF-8.
• Item and reference attachments are not exported. Have not been able to recreate this in UI although technically supported. Related to Handle custom attachments in email exports #4772 .