Update the nullability attributes of OpenIddictRequest.Audiences/Resources to indicate that null values can be present in the returned array

src/OpenIddict.Abstractions/Primitives/OpenIddictParameter.cs

@@ -1097,7 +1097,7 @@ public readonly struct OpenIddictParameter : IEquatable<OpenIddictParameter>
             // a number or a boolean, return its string representation.
             JsonValueKind.String or JsonValueKind.Number or
             JsonValueKind.True   or JsonValueKind.False
-                => element.ToString()!,
+                => element.ToString(),
 
             _ => null
         };
@@ -1165,7 +1165,7 @@ public readonly struct OpenIddictParameter : IEquatable<OpenIddictParameter>
             // or a boolean, return an 1-item array with its string representation.
             JsonValueKind.String or JsonValueKind.Number or
             JsonValueKind.True   or JsonValueKind.False
-                => new string?[] { element.ToString()! },
+                => new string?[] { element.ToString() },
 
             // When the parameter is a JsonElement representing an array, return the elements as strings.
             JsonValueKind.Array => CreateArrayFromJsonElement(element),

src/OpenIddict.Abstractions/Primitives/OpenIddictRequest.cs

@@ -127,9 +127,9 @@ public class OpenIddictRequest : OpenIddictMessage
     /// <summary>
     /// Gets or sets the "audience" parameters.
     /// </summary>
-    public string[]? Audiences
+    public string?[]? Audiences
     {
-        get => (string[]?) GetParameter(OpenIddictConstants.Parameters.Audience);
+        get => (string?[]?) GetParameter(OpenIddictConstants.Parameters.Audience);
         set => SetParameter(OpenIddictConstants.Parameters.Audience, value);
     }
 
@@ -379,9 +379,9 @@ public class OpenIddictRequest : OpenIddictMessage
     /// <summary>
     /// Gets or sets the "resource" parameters.
     /// </summary>
-    public string[]? Resources
+    public string?[]? Resources
     {
-        get => (string[]?) GetParameter(OpenIddictConstants.Parameters.Resource);
+        get => (string?[]?) GetParameter(OpenIddictConstants.Parameters.Resource);
         set => SetParameter(OpenIddictConstants.Parameters.Resource, value);
     }