Inform about flatpak branch change

Distribution

LMDE 6

Package version

6.4.8

Graphics hardware in use

No response

Frequency

Always

Bug description

Inform users about Flatpak branch changes. If a Flatpak package wants to change branches, the updates will not be applied and no information will be provided.

Steps to reproduce

I noticed a problem with the recent Flatpak change from Minetest to Luanti.
Flatpak (command line) showed:
Info: app net.minetest.Minetest branch stable is end-of-life, in favor of org.luanti.luanti branch stable

The Flatpak is supposed to change the branch, but MintUpdate behaved as follows:

1. An update for 'Luanti' is shown.
2. Start update.
3. Short loading
4. An update for 'Luanti' is shown (back at 1, but nothing has changed).

After some tries, I did a manual flatpak update realizing the problem.

Expected behavior

If MintUpdate cannot apply an update, such as in this case due to a branch change, provide the user with feedback.
A message such as 'Update could not be applied' or 'Manual update required' would suffice.

Additional information

No response

Start by reproducing the Flatpak branch-change case described in the issue, using the Flatpak command-line output as the reference behavior. Trace MintUpdate's handling of the Luanti update and determine where an unapplied update can be detected; done means the user receives clear feedback when manual intervention is required.