Move publicID creation to Note.create

Before this commit, `Note.create()` did not return a complete object,
as the `publicId` property was missing.
This adds the generation of the property to the `create` method and
moves the actual generation code from the `NotesService`
to a utility method.

Signed-off-by: David Mehren <git@herrmehren.de>

src/notes/utils.ts

@@ -0,0 +1,17 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import base32Encode from 'base32-encode';
+import { randomBytes } from 'crypto';
+
+/**
+ * Generate publicId for a note.
+ * This is a randomly generated 128-bit value encoded with base32-encode using the crockford variant and converted to lowercase.
+ */
+export function generatePublicId(): string {
+  const randomId = randomBytes(128);
+  return base32Encode(randomId, 'Crockford').toLowerCase();
+}