Implemeted missing methods in core models. (#43)

Author: Kevin Hellemun

BunqSdk/Model/Core/Installation.cs

@@ -65,5 +65,25 @@ public string GetPublicKeyServerString()
         {
             return publicKeyServer.ServerPublicKey;
         }
+
+        public override bool AreAllFieldNull()
+        {
+            if (this.SessionToken != null)
+            {
+                return false;
+            }           
+            
+            if (this.id != null)
+            {
+                return false;
+            }
+            
+            if (this.publicKeyServer != null)
+            {
+                return false;
+            }
+
+            return true;
+        }
     }
 }

BunqSdk/Model/Core/SessionServer.cs

@@ -61,5 +61,30 @@ private static byte[] GenerateRequestBodyBytes(string apiKey)
 
             return Encoding.UTF8.GetBytes(BunqJsonConvert.SerializeObject(sessionServerRequestBody));
         }
+
+        public override bool AreAllFieldNull()
+        {
+            if (this.Id != null)
+            {
+                return false;
+            }
+
+            if (this.SessionToken != null)
+            {
+                return false;
+            }
+
+            if (this.UserCompany != null)
+            {
+                return false;
+            }
+
+            if (this.UserPerson != null)
+            {
+                return false;
+            }
+
+            return true;
+        }
     }
 }