Add PolySharp so we can use required and init keyword

src/Mollie.Api/Models/Customer/CustomerRequest.cs

@@ -17,21 +17,21 @@ public class CustomerRequest {
         /// Allows you to preset the language to be used in the payment screens shown to the consumer. When this parameter is not 
         /// provided, the browser language will be used instead in the payment flow (which is usually more accurate).
         /// </summary>
-        public string Locale { get; set; }
+        public string? Locale { get; set; }
 
         /// <summary>
         /// Optional - Provide any data you like in JSON notation, and we will save the data alongside the customer. Whenever
         /// you fetch the customer with our API, we'll also include the metadata. You can use up to 1kB of JSON.
         /// </summary>
         [JsonConverter(typeof(RawJsonConverter))]
-        public string Metadata { get; set; }
+        public string? Metadata { get; set; }
 
         /// <summary>
         ///	Oauth only - Optional – Set this to true to make this customer a test customer.
         /// </summary>
         public bool? Testmode { get; set; }
 
-        public void SetMetadata(object metadataObj, JsonSerializerSettings jsonSerializerSettings = null) {
+        public void SetMetadata(object metadataObj, JsonSerializerSettings? jsonSerializerSettings = null) {
             this.Metadata = JsonConvert.SerializeObject(metadataObj, jsonSerializerSettings);
         }
     }

src/Mollie.Api/Mollie.Api.csproj

@@ -23,6 +23,10 @@
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="7.0.0" />
     <PackageReference Include="Microsoft.Extensions.Http.Polly" Version="7.0.10" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+    <PackageReference Include="PolySharp" Version="1.14.1">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
     <PackageReference Include="System.Runtime.Serialization.Primitives" Version="4.3.0" />    
   </ItemGroup>
 

src/Mollie.Api/Options/MollieOptions.cs

@@ -6,22 +6,22 @@ public record MollieOptions {
         /// <summary>
         /// Your API-key or OAuth token
         /// </summary>
-        public string ApiKey { get; set; } = null!;
+        public string ApiKey { get; set; } = string.Empty;
 
         /// <summary>
         /// (Optional) ClientId used by Connect API
         /// </summary>
-        public string ClientId { get; set; }
+        public string ClientId { get; set; } = string.Empty;
 
         /// <summary>
         /// (Optional) ClientSecret used by Connect API
         /// </summary>
         /// <returns></returns>
-        public string ClientSecret { get; set; }
+        public string ClientSecret { get; set; } = string.Empty;
 
         /// <summary>
         /// (Optional) Polly retry policy for failed requests
         /// </summary>
-        public IAsyncPolicy<HttpResponseMessage> RetryPolicy { get; set; }
+        public IAsyncPolicy<HttpResponseMessage>? RetryPolicy { get; set; }
     }
 }