Addressed a ISO date+time decoding issue inside the "decode(_:)" method for the ISOTimestampTranscoder transcoder in the library target.

Sources/AmiiboService/Internal/Transcoders/ISOTimestampTranscoder.swift

@@ -40,9 +40,17 @@ extension ISOTimestampTranscoder: DateTranscoder {
     
     /// Decodes an ISO timestamp string into a date.
     /// - Parameter string: A string to decode.
-    /// - Returns: A date parsed from the string, or the Unix epoch if the string cannot be parsed.
+    /// - Returns: A date parsed from the string.
+    /// - Throws: A `DecodingError` if the string cannot be parsed into a valid date.
     func decode(_ string: String) throws -> Date {
-        dateFormatter.date(from: string) ?? .init()
+        guard let date = dateFormatter.date(from: string) else {
+            throw DecodingError.dataCorrupted(.init(
+                codingPath: [],
+                debugDescription: "Expected an ISO timestamp with format 'yyyy-MM-dd'T'HH:mm:ss.SSSSSS', but found '\(string)' instead."
+            ))
+        }
+        
+        return date
     }
     
 }