Find all datasets that share a layer

[fm3]

Many datasets share a layer (e.g. one color layer, many segmentation layers)
wk should detect this (by resolving symlinks or the paths in datasource-properties.json) and store this information in postgres so that queries can be possible against this info (e.g. list all datasets with this layer)

[fm3]

This info could also be used when deleting datasets. If the layer is still referenced by another dataset (e.g. created via compose), the data should be moved, and other references/symlinks changed

[fm3]

@frcroth I don’t have a concrete design in mind for this yet. I guess we could store some property like “realpath” with the layers (or mags?) in postgres. We’d have to create a way for that information to get there. We’d have to deal with remote dataset layers.
The main use case right now is deletion #8279 – so remote datasets may not be the most important part right now.
I can show you around the existing code on dataset reporting from the datastore to postgres. Maybe you could then consider some ideas for how to solve this :)