Migration for transforming all image data-URLs
In conjunction with #37 (closed), #38 (closed), and dmx-projects/zukunftswerk#213 a Linqa migration is needed that transforms all image data-URLs as appearing in Notes, Textblocks, and Comments.
For every data-URL: an actual image file needs to be constructed from the embedded binary data and stored in the file repo, possibly scaled down. The data-URL must be replaced by the corresponding "normal" URL.
@jpn FYI