Add max length truncation to displayed profile attributes to mitigate spam

Changelog-Fixed: Add max length truncation to displayed profile attributes to mitigate spam
Fixes: #1237

damus/Util/StringUtil.swift

@@ -0,0 +1,34 @@
+//
+//  StringUtil.swift
+//  damus
+//
+//  Created by Terry Yiu on 6/4/23.
+//
+
+import Foundation
+
+extension String {
+    /// Returns a copy of the String truncated to maxLength and "..." ellipsis appended to the end,
+    /// or if the String does not exceed maxLength, the String itself is returned without truncation or added ellipsis.
+    func truncate(maxLength: Int) -> String {
+        guard count > maxLength else {
+            return self
+        }
+
+        return self[...self.index(self.startIndex, offsetBy: maxLength - 1)] + "..."
+    }
+}
+
+extension AttributedString {
+    /// Returns a copy of the AttributedString truncated to maxLength and "..." ellipsis appended to the end,
+    /// or if the AttributedString does not exceed maxLength, nil is returned.
+    func truncateOrNil(maxLength: Int) -> AttributedString? {
+        let nsAttributedString = NSAttributedString(self)
+        if nsAttributedString.length < maxLength { return nil }
+
+        let range = NSRange(location: 0, length: maxLength)
+        let truncatedAttributedString = nsAttributedString.attributedSubstring(from: range)
+
+        return AttributedString(truncatedAttributedString) + "..."
+    }
+}