private: adds tokens controller

adds private api
adds AuthTokenDto and AuthTokenWithSecretDto
adds necessary methods in the users service
adds RandomnessError

Signed-off-by: Philip Molares <philip.molares@udo.edu>

src/users/auth-token-with-secret.dto.ts

@@ -0,0 +1,13 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { IsString } from 'class-validator';
+import { AuthTokenDto } from './auth-token.dto';
+
+export class AuthTokenWithSecretDto extends AuthTokenDto {
+  @IsString()
+  secret: string;
+}