Don't lose map options when upgrading or codepush-ing

[bengtan]

From https://github.com/hippware/collaboration/issues/22#issuecomment-586364539:

User has the map orientation set to satellite, the user updates the app and the orientation has now reverted back to the default.

I believe this is referring to the mapOptions setting in HomeStore. It's lost upon upgrade (or codepush). It'd be nice to preserve it across upgrade or codepush.

[southerneer]

Whatever solution we come up with should be capable of generalizing to other pieces of local state that we want to survive across upgrades/codepushes since this kind of request will inevitably come up again.

[bengtan]

Here's some past history that's probably relevant.

There was a ticket ...

• Invisible mode might prematurely end after a codepush or upgrade Invisible mode might prematurely end after a codepush or upgrade #3753

... which had a similar problem.

There was a discussion ...

• Store user preferences that do not get deleted after upgrade or codepush Store user preferences that do not get deleted after upgrade or codepush #4410

... on how to fix it.

There was some talk about (creating and) preserving a dedicated part (ie. 'settingsStore'?) of the MST tree across upgrades. But this was short-circuited by just storing in clientData instead.

So, for this ticket, I guess we could revive the discussion about 'settingsStore' or just store it in clientData.

[aksonov]

@bengtan Yes, I solved it in the same way as I did with 'invisible' mode before.

[bengtan]

QA notes:

This ticket should be tested by upgrading from a version which already includes this ticket.