Discover screen in SwiftUI

[martindsq]

Closes #587 and #1066

• Implement DiscoverView
• Implement a reusable InfinitGrid mimiking InfiniteList but using a Grid instead
• Implement SearchResultsView reusing UniversalSearchResults (that is coupled by UIKit) as much as possible
• Implement identity and message cards that can be used by the InfinitGrid
• Refactor Message and Identity views to reuse code that loads the needed info from sqlite. Right now I defined CompactIdentityView and CompactPostView to use them in lists and GoldenIdentityView and GoldenPostView to use them in grids, so lets better share duplicate code to match something like:

graph TD
    AB[MessageButton] --> A
    A[MessageCard] --> B{Content}
    B --> |Contact|E
    B --> |Post|D{Style}
    D --> |Compact|I[CompactPostView]
    D --> |Post|K[GoldenPostView]
    EB[IdentityButton] --> E
    E[IdentityCard] --> F{Style}
    F --> |Compact|J[GoldenPostView]
    F --> |Golden|L[GoldenIdentityView]

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Bonus:

• Make the search to use profile's bios when filtering

[mplorentz]

This looks really nice. I left a few comments. I found myself wishing for more SwiftUIPreviews. I know we don't have a great way to add preview data to the FakeBot. Maybe we need PreviewBot that loads Feed_big.sqlite or something. But that's probably a task for the future.

[martindsq]

Thanks for looking at this.
As a general comment, I agree with you on the previews. I'm adding preview in each view I create as a general rule. The last refactor around the hierarchy of CompactIdentityView and CompactPostView (and moved the source of truth one level above) had the big advantage that I could play with different values in the previews.
However, once we reach the view that has the source of truth, we lose this capability. I'd love to do that, I already thought about it and I left it as it is because of the damn BotRepository we have now, once we get rid if that and use Bot directly, it will be a breeze to have a StubBot or a FakeBot with prefilled data.

[mplorentz]

This looks great. I see your point about changing BotRepository to just be a Bot. Let's try to prioritize that after the retreat.