config: splits config in multiple files

splits the big appConfig in multiple configs
adds media.config.mock.ts

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

src/config/csp.config.ts

@@ -0,0 +1,37 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import * as Joi from 'joi';
+import { registerAs } from '@nestjs/config';
+
+export interface CspConfig {
+  enable: boolean;
+  maxAgeSeconds: number;
+  includeSubdomains: boolean;
+  preload: boolean;
+}
+
+const cspSchema = Joi.object({
+  enable: Joi.boolean().default(true).optional(),
+  reportURI: Joi.string().optional(),
+});
+
+export default registerAs('cspConfig', async () => {
+  const cspConfig = cspSchema.validate(
+    {
+      enable: process.env.HD_CSP_ENABLE || true,
+      reportURI: process.env.HD_CSP_REPORTURI,
+    },
+    {
+      abortEarly: false,
+      presence: 'required',
+    },
+  );
+  if (cspConfig.error) {
+    throw new Error(cspConfig.error.toString());
+  }
+  return cspConfig.value;
+});