fix: use nanoid instead of shortid

shortid is deprecated and they recommend nanoid instead.
We're not sure if this has to do with possible name
collisions or enumerability, but to be sure and on the
safe side, we're changing this. nanoid seems quite safe
since it uses node's crypto module underneath.

Signed-off-by: Erik Michelson <github@erik.michelson.eu>

package.json

@@ -72,6 +72,7 @@
     "moment": "2.30.1",
     "morgan": "1.10.0",
     "mysql2": "3.14.0",
+    "nanoid": "3.3.11",
     "node-fetch": "2.7.0",
     "passport": "patch:passport@npm%3A0.7.0#~/.yarn/patches/passport-npm-0.7.0-df02531736.patch",
     "passport-dropbox-oauth2": "1.1.0",
@@ -95,7 +96,6 @@
     "sanitize-filename": "1.6.3",
     "scrypt-kdf": "2.0.1",
     "sequelize": "5.22.5",
-    "shortid": "2.2.17",
     "socket.io": "2.5.1",
     "sqlite3": "5.1.7",
     "store": "2.0.12",