mute: adding new structs/enums for new mute list

- Adding MuteItem & DamusDuration
- Changing RefId hashtag associated type from TagElem to Hashtag
    - This is done because in MuteItem, we can not create a RefId.hashtag TagElem instance since we don’t have a note associated with a given hashtag mute item.

Related: https://github.com/damus-io/damus/issues/1718
Related: https://github.com/damus-io/damus/issues/856
Lighting Address: fishcharlie@strike.me

Signed-off-by: Charlie Fish <contact@charlie.fish>
Reviewed-by: William Casarin <jb55@jb55.com>
Signed-off-by: William Casarin <jb55@jb55.com>

damus/Types/DamusDuration.swift

@@ -0,0 +1,38 @@
+//
+//  DamusDuration.swift
+//  damus
+//
+//  Created by Charlie Fish on 1/13/24.
+//
+
+import Foundation
+
+enum DamusDuration: CaseIterable {
+    case day
+    case week
+    case month
+
+    var title: String {
+        switch self {
+        case .day:
+            return NSLocalizedString("24 hours", comment: "A duration of 24 hours/1 day to be shown to the user. Most likely in the context of how long they want to mute a piece of content for.")
+        case .week:
+            return NSLocalizedString("1 week", comment: "A duration of 1 week to be shown to the user. Most likely in the context of how long they want to mute a piece of content for.")
+        case .month:
+            return NSLocalizedString("1 month", comment: "A duration of 1 month to be shown to the user. Most likely in the context of how long they want to mute a piece of content for.")
+        }
+    }
+
+    var date_from_now: Date? {
+        let current_date = Date()
+
+        switch self {
+        case .day:
+            return Calendar.current.date(byAdding: .day, value: 1, to: current_date)
+        case .week:
+            return Calendar.current.date(byAdding: .day, value: 7, to: current_date)
+        case .month:
+            return Calendar.current.date(byAdding: .month, value: 1, to: current_date)
+        }
+    }
+}