Implemented permission updateing

ref #6

src/errors/PermissionErrors.ts

@@ -22,4 +22,15 @@ export class PermissionIdsNotMatchingError extends NotAcceptableError {
 
 	@IsString()
 	message = "The id's don't match!! \n And if you wanted to change a permission's id: This isn't allowed"
+}
+
+/**
+ * Error to throw when a permission get's provided without a principal.
+ */
+export class PermissionNeedsPrincipalError extends NotAcceptableError {
+	@IsString()
+	name = "PermissionNeedsPrincipalError"
+
+	@IsString()
+	message = "You provided no principal for this permission."
 }