[mhammond]

This is towards allowing per-device or per-account settings, driven by the app - a replacement for #7611. This is a breaking change:

• Add FXIOS-17055 [Sync] Per-device Sync engine enablement logic mozilla-mobile/firefox-ios#36006
• https://bugzilla.mozilla.org/show_bug.cgi?id=2082379

[mhammond]

pushing a new version of this:

• the new enum type EngineChoicesModel is in sync15 crate, import might change.
• EngineChoicesModel::Device variant no longer has the enabled engines.
• SyncParams::device_settings has a new enabled_engines with that info, should be filled unconditionally in all worlds.

[lougeniaC64]

pushing a new version of this:

* the new enum type `EngineChoicesModel` is in sync15 crate, import might change.

* `EngineChoicesModel::Device` variant no longer has the enabled engines.

* `SyncParams::device_settings` has a new `enabled_engines` with that info, should be filled unconditionally in all worlds.

@mhammond Do you expect you'll need to make additional changes to this PR? If so it might make sense for Robin and I to pivot to other work in the meantime. @bytesized

[mhammond]

oops, I think I pushed a badly rebased version of this; updated to just be simple type changes and no logic - I think it's looking good to land. I linked an Android fix, and iOS will need to update where current options are listed. Once we have r+ everywhere we can talk to relman and land them all 🤞