Stable randomized per-app advertising ID

Is your feature request related to a problem? Please describe.
If an app were to fingerprint a device, its algorithm may be fooled by microG's randomization of the advertising ID, but it also could be easily detected by just checking if it changes right away and it can then ignore it.

Describe the solution you'd like
As an alternative to the advertising ID full on randomization, my suggestion would be to have stable but still randomized IDs returned for each app, that way they can't tell the advertising ID is randomized. If keeping a database of these is undesirable, then I believe hashing could help, e.g. hash(uniqueValue.. appPackageName.. appSigningKey)

Describe alternatives you've considered
Nothing

Additional context
This does have the potential of making detection even stronger and then they may start detecting microG instead.

Also if an app were to use the advertising ID just to keep track of activity within itself, it would still be able to do that

No file, test, or entry point is named. Start by locating microG's advertising ID implementation and reading how IDs are currently randomized. Done means the behavior is stable per app, still randomized, difficult to detect as randomized, and preserves the stated intra-app tracking behavior.