Make the JsonConverters for delimited arrays more generic (#13396)

* Make the JsonConverters for delimited arrays more generic

Also adds some tests for serialization (with different types) as we didn't have any before.

* Ignore warnings

tests/Jellyfin.Extensions.Tests/Json/Models/GenericBodyIReadOnlyCollectionModel.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+using Jellyfin.Extensions.Json.Converters;
+
+namespace Jellyfin.Extensions.Tests.Json.Models
+{
+    /// <summary>
+    /// The generic body <c>IReadOnlyCollection</c> model.
+    /// </summary>
+    /// <typeparam name="T">The value type.</typeparam>
+    public sealed class GenericBodyIReadOnlyCollectionModel<T>
+    {
+        /// <summary>
+        /// Gets or sets the value.
+        /// </summary>
+        [JsonConverter(typeof(JsonCommaDelimitedCollectionConverterFactory))]
+        public IReadOnlyCollection<T> Value { get; set; } = default!;
+    }
+}