Add TLS certificate password support for MQTTnet.Server.

Source/MQTTnet.Server/Configuration/CertificateSettingsModel.cs

@@ -0,0 +1,35 @@
+using System.IO;
+
+namespace MQTTnet.Server.Configuration
+{
+    public class CertificateSettingsModel
+    {
+        /// <summary>
+        /// Path to certificate.
+        /// </summary>
+        public string Path { get; set; }
+        
+        /// <summary>
+        /// Password of certificate.
+        /// </summary>
+        public string Password { get; set; }
+
+        /// <summary>
+        /// Read certificate file.
+        /// </summary>
+        public byte[] ReadCertificate()
+        {
+            if (string.IsNullOrEmpty(Path) || string.IsNullOrWhiteSpace(Path))
+            {
+                throw new FileNotFoundException("No path set");
+            }
+
+            if (!File.Exists(Path))
+            {
+                throw new FileNotFoundException($"Could not find Certificate in path: {Path}");
+            }
+
+            return File.ReadAllBytes(Path);
+        }
+    }
+}