Address minor build warnings

Author: kzu

src/TableStorage.Bson/BsonDocumentSerializer.cs

@@ -58,7 +58,7 @@ public byte[] Serialize<T>(T value)
         class DateOnlyJsonConverter : JsonConverter<DateOnly>
         {
             public override DateOnly ReadJson(JsonReader reader, Type objectType, DateOnly existingValue, bool hasExistingValue, JsonSerializer serializer)
-                => DateOnly.Parse((string)reader.Value, CultureInfo.InvariantCulture);
+                => DateOnly.Parse((string)reader.Value!, CultureInfo.InvariantCulture);
 
             public override void WriteJson(JsonWriter writer, DateOnly value, JsonSerializer serializer)
                 => writer.WriteValue(value.ToString("O", CultureInfo.InvariantCulture));

src/TableStorage.MessagePack/MessagePackDocumentSerializer.cs

@@ -42,7 +42,7 @@ public MessagePackDocumentSerializer(MessagePackSerializerOptions? options = def
         public byte[] Serialize<T>(T value) => value == null ? new byte[0] : MessagePackSerializer.Serialize(value.GetType(), value, options);
 
 #if NET6_0_OR_GREATER
-        class DateOnlyFormatterResolver : IFormatterResolver
+        internal class DateOnlyFormatterResolver : IFormatterResolver
         {
             public static IFormatterResolver Instance = new DateOnlyFormatterResolver();
 
@@ -54,7 +54,7 @@ public IMessagePackFormatter<T> GetFormatter<T>()
                 return null!;
             }
 
-            class DateOnlyFormatter : IMessagePackFormatter<DateOnly>
+            internal class DateOnlyFormatter : IMessagePackFormatter<DateOnly>
             {
                 public static readonly IMessagePackFormatter<DateOnly> Instance = new DateOnlyFormatter();