Avoid changing intro dictionary in HTTP controller

ConfusedPolarBear.Plugin.IntroSkipper/Controllers/SkipIntroController.cs

@@ -54,7 +54,8 @@ public class SkipIntroController : ControllerBase
     /// <returns>Intro object if the provided item has an intro, null otherwise.</returns>
     private Intro? GetIntro(Guid id)
     {
-        return Plugin.Instance!.Intros.TryGetValue(id, out var intro) ? intro : null;
+        // Returns a copy to avoid mutating the original Intro object stored in the dictionary.
+        return Plugin.Instance!.Intros.TryGetValue(id, out var intro) ? new Intro(intro) : null;
     }
 
     /// <summary>

ConfusedPolarBear.Plugin.IntroSkipper/Data/Intro.cs

@@ -32,6 +32,17 @@ public class Intro
         IntroEnd = 0;
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Intro"/> class.
+    /// </summary>
+    /// <param name="intro">intro.</param>
+    public Intro(Intro intro)
+    {
+        EpisodeId = intro.EpisodeId;
+        IntroStart = intro.IntroStart;
+        IntroEnd = intro.IntroEnd;
+    }
+
     /// <summary>
     /// Initializes a new instance of the <see cref="Intro"/> class.
     /// </summary>