Add experimental push notification support

I added support for the experimental push notifications feature. There are many improvements to be made, so this feature is currently opt-in only. If the user does not opt-in, their device tokens will not be sent out and thus they will receive no push notifications.

We should perform more testing on real-life staging environments before fully releasing this feature.

Testing
-------

Testing was done gradually during development.

Device: iOS simulators
iOS: 17
Damus version: A few different but recent prototypes
Rough coverage:
1. Checked that no device tokens are sent out when setting is off
2. Checked that I can successfully receive device tokens when feature is ON and set to localhost.
3. Checked sending test push notifications of types "note" (kind: 1), reaction (kind: 7) and DMs (kind 4) works and shows a generic but reasonable push notification message
4. Checked that clicking on the notifications above take the user to the correct screen

Closes: https://github.com/damus-io/damus/issues/67
Changelog-Added: Add experimental push notification support
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
Signed-off-by: William Casarin <jb55@jb55.com>

damus/ContentView.swift

@@ -54,6 +54,7 @@ enum Sheets: Identifiable {
 
 struct ContentView: View {
     let keypair: Keypair
+    let appDelegate: AppDelegate?
     
     var pubkey: Pubkey {
         return keypair.pubkey
@@ -303,6 +304,7 @@ struct ContentView: View {
                 active_sheet = .onboardingSuggestions
                 hasSeenOnboardingSuggestions = true
             }
+            self.appDelegate?.settings = damus_state?.settings
         }
         .sheet(item: $active_sheet) { item in
             switch item {
@@ -694,7 +696,7 @@ struct ContentView: View {
 
 struct ContentView_Previews: PreviewProvider {
     static var previews: some View {
-        ContentView(keypair: Keypair(pubkey: test_pubkey, privkey: nil))
+        ContentView(keypair: Keypair(pubkey: test_pubkey, privkey: nil), appDelegate: nil)
     }
 }