Add project files

StalwartSimpleLoginMiddleware/Services/StalwartClient.cs

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+using AdOrbitSDK;
+using StalwartSimpleLoginMiddleware.Constants;
+
+namespace StalwartSimpleLoginMiddleware.Services;
+
+public class StalwartClient() : IDisposable
+{
+    private Client _userClient;
+
+    private static HttpClient HttpClient => new()
+    {
+        BaseAddress = new Uri(Environment.GetEnvironmentVariable(EnvironmentVariable.MailServerUri) + "/api/")
+    };
+
+    public async Task<Client> GetClient()
+    {
+        if (_userClient != null) return _userClient;
+
+        return GetClient(Environment.GetEnvironmentVariable(EnvironmentVariable.MailServerApiKey) ?? string.Empty);
+    }
+
+    private Client GetClient(string apiKey)
+    {
+        if (_userClient != null) return _userClient;
+
+        if (string.IsNullOrEmpty(HttpClient.BaseAddress?.AbsoluteUri))
+            throw new NullReferenceException($"{EnvironmentVariable.MailServerUri} is missing in environment.");
+
+        if (string.IsNullOrEmpty(apiKey))
+            throw new NullReferenceException($"{EnvironmentVariable.MailServerApiKey} is missing in environment.");
+
+        _userClient = new Client(HttpClient, apiKey);
+        return _userClient;
+    }
+
+    public void Dispose()
+    {
+        HttpClient.Dispose();
+        GC.SuppressFinalize(this);
+    }
+}