refactor(RSACryptographer): Interne Methoden zur Konfiguration von RSACryptographen hinzugefügt.

- IsPemNull.get-Methode hinzugefügt, um zu prüfen, ob _pem null ist.
 - SetPem-Methode hinzugefügt, um pem im Projekt aktualisieren zu können.

DigitalData.Core.Security/Cryptographer/RSACryptographer.cs

@@ -14,6 +14,8 @@ namespace DigitalData.Core.Security.Cryptographer
             init => _pem = value;
         }
 
+        internal bool IsPemNull => _pem is null;
+        
         public string? PemPath => FileName is null ? null : Path.Combine(Directory ?? string.Empty, FileName);
 
         public string? Directory { get; set; }
@@ -29,7 +31,9 @@ namespace DigitalData.Core.Security.Cryptographer
         public string Audience { get; init; } = string.Empty;
 
         internal RSACryptographer() { }
-        
+
+        internal void SetPem(string pem) => _pem = pem;
+
         public virtual void UnableToInitPemEvent() => throw new InvalidOperationException(
             $"Pem is not initialized and pem file is null. Issuer is {Issuer} and audience {Audience}.");