[QGIS-Developer] Offline layer

[matteo]

Hi Harrissou,

that's a good question. From what I understood the icon/flag is added 
"manually" when needed (by QFieldSync, Offline editing plugin, etc).

Not sure how/when it should removed: maybe changing the data source is 
still pointing to an offline layer.

At the beginning I was thinking that if a layer was "converted" to 
offline and for example put into a geopackage, then some additional 
metadata were added in some additional table within the geopackage itself.

But now I understand that the flag is manually added by the developer

Cheers

Matteo