Doc: scripts for manual registration + improve reset password (#459)

* T.: Document ways for resetting passwords just w standard shell utils

* T.: Document manual user registration

* T.: Improved string escapes in our scripts

* T.: Don't change this file

* T.: Add newline

docs/register-user.md

@@ -0,0 +1,29 @@
+# Registering users manually
+
+You might want to disable registration in your [instance config](/configuration), but still have a quick way to manually register users upon request. To do so, first set up a separate instance that only listens on localhost, has registration enabled,
+and captchas as well as background jobs disabled. Make sure you have a way to start it easily with just one or a few commands, e.g. via a systemd service. Then, use something like the script below (in the example, the instance is started via a systemd
+service called `podman-invidious_register`, and it listens on localhost port 21742. **Warning**: This script is vulnerable to SQL injections. Only use trusted inputs; if you want to make a custom signup form and use this as a backend, be sure to
+sanitize inputs.
+```sh
+#!/usr/bin/env bash
+set -e
+
+systemctl start podman-invidious_register
+
+CONTINUE='y'
+while [ "$CONTINUE" = 'y' ]; do
+    read -rp 'User ID: ' ID
+    if [ "$(su postgres -c "psql invidious -c \"SELECT email FROM users WHERE email = '\"'$ID'\"';\"" | tail -n 2 | head -n 1)" != '(0 rows)' ]; then
+        echo 'Error: User ID is already taken'
+        continue
+    fi
+
+    read -rsp 'Password: ' PASSWORD
+
+    curl -L 'http://localhost:21742/login' --form-string "email=$ID" --form-string "password=$PASSWORD" -F 'action=signin' >/dev/null
+
+    read -rp 'Register more accounts? [y/N] ' CONTINUE
+done
+
+systemctl stop podman-invidious_register
+```

docs/reset-password.md

@@ -4,10 +4,11 @@ Resetting a user's invidious password needs you to edit the database.
 
 Firstly, generate a bcrypt-encrypted hash for the new password you want to set for the user.
 
-This can be done with the `bcrypt` python module, though there are other ways of doing the same.
+This can, for example, be done with the `bcrypt` python module or the `mkpasswd` shell utility (the latter should be preinstalled on most systems):
 
 ```
-python3 -c 'import bcrypt; print(bcrypt.hashpw(b"<INSERT PASSWORD HERE>", bcrypt.gensalt(rounds=10)).decode("ascii"))'
+python3 -c 'import bcrypt; print(bcrypt.hashpw(b"<INSERT PASSWORD HERE>", bcrypt.gensalt(rounds=10)).decode("ascii"))' # python
+mkpasswd --method=bcrypt-a -R 10 # mkpasswd
 ```
 
 To do so, first attach to the database:
@@ -23,3 +24,19 @@ UPDATE users SET password = 'HASH' WHERE email = 'USERNAME';
 ```
 
 After that, the password should be reset.
+
+This script bundles all needed commands so you don't have to enter everything manually every time, and also checks that the username exists before writing to the database:
+```sh
+#!/bin/sh
+set -e
+
+printf 'User ID: '
+read -r ID
+if [ "$(su postgres -c "psql invidious -c \"SELECT email FROM users WHERE email = '$ID';\"" | tail -n 2 | head -n 1)" != '(1 row)' ]; then
+    echo 'Error: User ID does not exist'
+    exit 1
+fi
+
+HASH="$(mkpasswd --method=bcrypt-a -R 10)"
+su postgres -c "psql invidious -c \"UPDATE users SET password = '\"'$HASH'\"' WHERE email = '\"'$ID'\"';\""
+```