Related to #2780 (fixes the first part of the issue)
During attachment upload Pleroma returns a "description" field. Pleroma-fe uses that to pre-fill the image description field, pleroma-fe!1399 (merged).
- This MR allows Pleroma to read the EXIF data during upload and return a relevant description to the FE based on the specific EXIF fields for caption and description
- If a description is already present (e.g. because a previous module added it), it will use that
- Otherwise it will read from the EXIF data. First it will check -ImageDescription, if that's empty, it will check -iptc:Caption-Abstract. If someone with more knowledge in these things believes other fields or order should be used, please let me know. Otherwise it can always be changed in a later MR if that turns out to be needed.
- If no description is found, the module will simply return nil, which is the value it had before
- When people set up a new instance, they will be asked if they want to use the EXIF data for this and this module will be activated if so.
In a later MR I want to make it possible to write the description to the EXIF data. That way image descriptions will be more portable (i.e. you can download an image, re-upload it, and image descriptions will remain intact), see #2780.