add admin command to delete all remote media files

src/service/media.rs

@@ -141,6 +141,15 @@ impl Service {
         Ok(())
     }
 
+    /// List all media stored in the database.
+    ///
+    /// Each MXC is list once. Thumbnails are not included separately from the
+    /// original media.
+    #[tracing::instrument(skip(self))]
+    pub(crate) fn iter_all(&self) -> impl Iterator<Item = Result<OwnedMxcUri>> {
+        self.db.all_file_metadata().map(|media| media.map(|(mxc, ..)| mxc))
+    }
+
     /// Returns width, height of the thumbnail and whether it should be cropped.
     /// Returns None when the server should send the original file.
     fn thumbnail_properties(