Handle fractional dates

Navidrome returns these, but other servers may not.
NSISO8601DateFormatter looks like it can parse one or the other, but not
both with the same instance. So, have two.

README.md

@@ -38,6 +38,7 @@ Doing so isn't fatal (it's not a secret), but it is annoying for other contribut
 * The playlist model has been corrected to handle multiple of the same track. (GH-192)
 * Lower case artist names are properly sorted in the artist list.
 * Favouriting items is available from the menu bar, or Cmd+E.
+* Fix parsing fractional dates returned by some servers.
 * Fix the null cover being used for system now playing information.
 * Upgrading from Submariner 1.x is no longer supported.
 

Submariner/String+Time.swift

@@ -10,6 +10,14 @@ import Cocoa
 
 extension String {
     fileprivate static let iso8601Formatter = ISO8601DateFormatter()
+    // Navidrome returns fractional time, but ISO8601DateFormatter will reject it.
+    // The .withFractionalSeconds option is what we want, but it mandates fractional seconds then.
+    // Have two formatters to try to use. To have one is blocking on FB13972481.
+    fileprivate static let iso8601FractionalFormatter: ISO8601DateFormatter = {
+        let formatter = ISO8601DateFormatter()
+        formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+        return formatter
+    }()
     fileprivate static let rfc3339DateFormatter: DateFormatter = {
         let formatter = DateFormatter()
         formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
@@ -26,7 +34,7 @@ extension String {
     }()
 
     func dateTimeFromISO() -> Date? {
-        return String.iso8601Formatter.date(from: self as String)
+        return String.iso8601Formatter.date(from: self as String) ?? String.iso8601FractionalFormatter.date(from: self as String)
     }
 
     func dateTimeFromRFC3339() -> Date? {