Support Additional XMP tags created by AnalogEXIF

[rexbron]

Is your feature request related to a problem? Please describe.
Add support for the following XMP Tags to support hybrid analog/digital workflows. Some of these tags are obsolete but it would be good to support them for backwards compatibility.

Samples

Example:

Xmp.aux.SerialNumber                         XmpText     7  2469312
Xmp.aux.Lens                                 XmpText     9  Summicron

Describe the solution you'd like
Add support for these tags to Darktable

[ralfbrown]

Pending #18036 will allow adding any supported tag to the metadata editor. However, Exiv2 will also need to support those tags before darktable can use them, since it relies on libexiv2 to retrieve metadata tags from the image file.

[zisoft]

This is a good test for #18036

Search for the tags in the metadata preferences, both are listed and thus supported by exiv2:

Added them and now they appear in the metadata editor and can be filled:

Exported the image and checked for the tags:

~/Desktop exiv2 -p a -g aux mire1.jpg
Xmp.aux.Lens                                 XmpText     9  Summicron
Xmp.aux.SerialNumber                         XmpText     7  2469312

Now the other way around: Imported the just exported image to darktable and see the tags are imported as well: