Add more details and warnings

| Institut für Computerlinguistik | `ldaps://ldap2.cl.uni-heidelberg.de` | CL account |

| Universität Heidelberg | `ldaps://ad.uni-heidelberg.de` | Uni ID |

## Fundamental reading

If you have not worked with LDAP before, I strongly recommend reading the following Stack Overflow question:

[**How to safely authenticate a user using LDAP?**](https://stackoverflow.com/questions/73681632/how-to-safely-authenticate-a-user-using-ldap/)

It explains how authentication via LDAP is generally done (which is a bit weird compared to many modern computer systems), how it can be done safely, and also discusses a few quirks and special cases of different LDAP servers.

## Create server object

server = Server(ldap_server_url, use_ssl=True)

```

>>> [!warning]

Binding to the Uni LDAP server currently does not require the TLS certificate to be valid. This is a security issue, because any attacker could just Man-in-the-Middle the connection and eavesdrop on all sent usernames and passwords.

I currently discourage using the Uni LDAP server, until I have figured out a better way to do this.

>>>

>>> [!note]

The URL scheme (`ldap://` or `ldaps://`) has precedence over the parameter `use_ssl` (see https://ldap3.readthedocs.io/en/latest/server.html). This means that the parameter is superfluous if you specify a URL scheme.

dn = f"cn={escape_rdn(user)},ou=fnphi,ou=rzuser,dc=ad,dc=uni-heidelberg,dc=de"

```

>>> [!important]

This only works if the student is part of the `ou=fnphi` organization, i.e., a member of the Neuphilologische Fakultät. This does not generalize. Until I've figured out a better way, I discourage using the Uni LDAP server.

>>>

## Connect

```python