Make more file-related metadata available in content-specific graphs
Our sandboxing model is that a photos app will only see the tracker:Pictures graph, a music app will only see the tracker:Audio graph, and so on.
GNOME Photos queries the filename, mtime and ctime of each photo in order to display this info in the UI. These are stored in the tracker:FileSystem graph as nfo:fileName, nfo:fileLastModified and nfo:fileCreated respectively.
Photos can request access to the tracker:FileSystem graph to fetch this data, but this means it can see the whole structure of the home directory as indexed by Tracker - this is exposing more data than the app needs to see.