Refactor(RSACryptographer): Entfernte Pem initter Methode.

- PrivateKeyPem initter Methode zu RSADecryptor hinzugefügt.
 - PublicKeyPem getter und initter Methoden zu RSAEncryptor hinzugefügt.

DigitalData.Core.Security/RSADecryptor.cs

@@ -1,9 +1,12 @@
-using System.Security.Cryptography;
-
-namespace DigitalData.Core.Security
+namespace DigitalData.Core.Security
 {
     public class RSADecryptor : RSACryptographer
     {
+        public required string PrivateKeyPem
+        {
+            init => _rsa.ImportFromPem(value);
+        }
+
         public string PublicKeyPem => _rsa.ExportRSAPublicKeyPem();
 
         public RSAEncryptor Encryptor
@@ -12,7 +15,7 @@ namespace DigitalData.Core.Security
             {
                 return new ()
                 {
-                    Pem = PublicKeyPem,
+                    PublicKeyPem = PublicKeyPem,
                     Padding = Padding
                 };
             }