[low priority] Userconfig versions - Agent allows flashing higher config versions.

[kareltucek]

Scenario:

• use a master agent with a master firmware. Assume 12.1.0 userconfig versions. Save config to UHK. Export the config. 12.1.0 UserConfig.json gets exported.
• start 8.0.1 (i.e., 12.0.0 UserConfig).
• flash the packed 15.3.0 firmware (it is a 12.0.1 firmwareBuiltUserconfig)
• reset device configuration (to bring down the flashd version down to 12.0.0)
• (so far so good)
• now import the 12.1.0 configuration exported above.
• save it to keyboard
• now we have a 12.0.1 firmwareBuiltUserconfig UHK with a 12.1.0 flashedUserconfig flashed from a 12.0.0 agentBuiltUserconfig

How did we get here? How did / could a 12.0.0 Agent import and save a 12.1.0 config?

Things to discuss / check and maybe fix:

• Did it indeed manage to save a valid 12.1.0 userconfig? (I mean, it doesn't know how to serialize the 12.1.0-specific things, so it must have at the very least thrown out some features, hasn't it?)
• It should probably not allow flashing a userconfig version that is higher than the firmwareBuiltUserconfig version.

(This has nothing to do with 2779 / 2780.)