WebDAV: Keep favorite flag when uploading via PhotoSync

[graciousgrey]

As a user, that uses PhotoSync in combination with PhotoPrism, I want photos that have been marked as favorite on my phone to be marked in PhotoPrism as well, so that I do not need to mark photos as favorite twice.

Acceptance Criteria:

• Mark a photo as favorite when it comes with the header
• Read Recordtime header in case the photo/video has no exif data
• Add unit tests
• Update documentation

[dror3go]

@graciousgrey is there a different way to get this favorite boolean other than a X- header prefix? This "custom header" prefix has been deprecated back in 2012.

[lastzero]

This has been released. Note that PhotoSync for Android might not send the required header yet, so it may only work on iOS so far.