fix some nullable reference types issues

Author: Bryan Aldrich

modules/openapi-generator/src/main/resources/csharp/auth/OAuthAuthenticator.mustache

@@ -13,9 +13,9 @@ namespace {{packageName}}.Client.Auth
     /// </summary>
     public class OAuthAuthenticator : IAuthenticator
     {
-        private TokenResponse? _token;
+        private TokenResponse{{nrt?}} _token;
 
-        public string? Token
+        public string{{nrt?}} Token
         {
             get
             {
@@ -90,8 +90,7 @@ namespace {{packageName}}.Client.Auth
         /// <returns>An authentication token.</returns>
         async Task<string> GetToken()
         {
-            var client = new RestClient(_tokenUrl,
-                configureSerialization: serializerConfig => serializerConfig.UseSerializer(() => new CustomJsonCodec(_serializerSettings, _configuration)));
+            var client = new RestClient(_tokenUrl, configureSerialization: serializerConfig => serializerConfig.UseSerializer(() => new CustomJsonCodec(_serializerSettings, _configuration)));
 
             var request = new RestRequest();
             if (!string.IsNullOrWhiteSpace(_token?.RefreshToken))
@@ -124,6 +123,6 @@ namespace {{packageName}}.Client.Auth
         }
 
         public async ValueTask Authenticate(IRestClient client, RestRequest request)
-                => request.AddOrUpdateParameter(await GetAuthenticationParameter().ConfigureAwait(false));
+            => request.AddOrUpdateParameter(await GetAuthenticationParameter().ConfigureAwait(false));
     }
 }

modules/openapi-generator/src/main/resources/csharp/auth/TokenResponse.mustache

@@ -16,7 +16,7 @@ namespace {{packageName}}.Client.Auth
         public DateTime Created { get; set; }
 
         [JsonProperty("refresh_token")]
-        public string? RefreshToken { get; set; }
+        public string{{nrt?}} RefreshToken { get; set; }
 
         public DateTime? ExpiresAt => ExpiresIn == null ? null : Created.AddSeconds(ExpiresIn.Value);
     }