Remember selected sorting options

[emmavray]

Checklist

• [X] I have described what this PR contains

Choose one of the following two options:

• • [X] This PR does not introduce major changes
• • [ ] This PR introduces major changes, and I have consulted @buresdv, @jboi or @mormaer in the Mlem Development Matrix room

Choose one of the following two options:

• • [X] This PR does not change the UI in any way
• • [ ] This PR adds new UI elements / changes the UI, and I have attached pictures or videos of the new / changed UI elements

Pull Request Information

About this Pull Request

This is a simple change to persist across app launches, using AppStorage:

• the currently selected SortingOptions for the feed and
• the currently selected FeedType (All Posts, Subscribed, etc)

Before this PR, each app launch will result in the feed resetting to the default Subscribed feed sorted by Hot. After this PR, the app will remember your last selected FeedType and SortingOptions.

Screenshots and Videos

There are no UI changes, it's completely transparent to the user.

Additional Context

This change was inspired by the last few days of using Mlem. As a new Lemmy user who hasn't subscribed to many communities, I prefer to browse the All Posts feed. The default Hot sort is not very useful in this case, as the content is essentially unchanged for the last several days. Remembering my last selected FeedType and SortingOptions lets me get right into the app and start browsing.

I considered adding a sort preference in Settings (to match the Default Comment Sort option that already exists). However I hesitate to add two different UIs for a single preference; it seems to me that allowing the user to pick their preferred sort in context makes a lot of sense, and it's reasonable to expect that the app would remember this preference. Happy to adjust the implementation if an explicit setting is preferred.

Similar for FeedType -- it just makes sense that the app would remember which feed you browse.

A note on NSUserDefault keys: it may be useful to consider scoping the preferences a bit more specifically. For example in the future it may be best to persist sort options (for example) for each applicable screen; user feeds may have a different preferred sort than the post feed. Or taking it a step further, users may expect All Posts to sort differently than Subscribed or Local feeds. I suggest a reverse-domain approach.

[emmavray]

certainly a UX change, IMO three ways to do it:

1. Don't persist the last feed/sort options, always use Subscribed and Hot (CURRENT BEHAVIOR)
2. Automatically persist the last used feed/sort options, and don't provide a user setting (THIS PR)
3. Add settings UIs to pick preferred feed and sort options, maybe including an option for Last Used

If a user setting is required it may make sense to have the default value of Last Used

[mormaer]

certainly a UX change, IMO three ways to do it:

1. Don't persist the last feed/sort options, always use Subscribed and Hot (CURRENT BEHAVIOR)
2. Automatically persist the last used feed/sort options, and don't provide a user setting (THIS PR)
3. Add settings UIs to pick preferred feed and sort options, maybe including an option for Last Used

If a user setting is required it may make sense to have the default value of Last Used

under Settings -> General (GeneralSettingsView) there is an option for comment sorting in there, I think it'd be best (for now) to add these additional ones alongside that as a first step?

[JakeShirley]

FWIW I feel like at some point we should save this setting per feed type like Apollo. Some communities I like to sort by new, some by hot, etc.

[ShadowJonathan]

Heya @cdstamper, we have a new repo at https://github.com/mlemgroup/mlem, due to some shuffling around we couldn't get it migrated properly, but if you could reopen this PR there, and link it back here, then it can continue to be considered ^^