Implemented permission updateing

ref #6

src/errors/PrincipalErrors.ts

@@ -0,0 +1,24 @@
+import { IsString } from 'class-validator';
+import { NotAcceptableError, NotFoundError } from 'routing-controllers';
+
+/**
+ * Error to throw when a user couldn't be found.
+ */
+export class PrincipalNotFoundError extends NotFoundError {
+	@IsString()
+	name = "PrincipalNotFoundError"
+
+	@IsString()
+	message = "Principal not found!"
+}
+
+/**
+ * Error to throw, when a provided runnerOrganisation doesn't belong to the accepted types.
+ */
+export class PrincipalWrongTypeError extends NotAcceptableError {
+	@IsString()
+	name = "PrincipalWrongTypeError"
+
+	@IsString()
+	message = "The princial must have an existing principal's id. \n You provided a object of another type."
+}