docs: restructure documentation

This rewrite follows the principles of https://diataxis.fr/

Co-authored-by: Erik Michelson <github@erik.michelson.eu>
Signed-off-by: Philip Molares <philip.molares@udo.edu>
Signed-off-by: Erik Michelson <github@erik.michelson.eu>

docs/content/how-to/develop/auth/ldap.md

@@ -0,0 +1,42 @@
+# LDAP
+
+If you are developing HedgeDoc and need to test something with an LDAP server you can use the
+[`test-openldap`][docker-image] Docker image from [rroemhild][rroemhild].
+
+Simply run
+
+<!-- markdownlint-disable proper-names -->
+```shell
+docker run --rm -p 10389:10389 -p 10636:10636 rroemhild/test-openldap
+```
+<!-- markdownlint-enable proper-names -->
+
+and add the following to the `.env` file then start the backend.
+
+```dotenv
+HD_AUTH_LDAP_SERVERS="FUTURAMA"
+HD_AUTH_LDAP_FUTURAMA_PROVIDER_NAME="Futurama LDAP"
+HD_AUTH_LDAP_FUTURAMA_URL="ldap://localhost:10389"
+HD_AUTH_LDAP_FUTURAMA_SEARCH_BASE="ou=people,dc=planetexpress,dc=com"
+HD_AUTH_LDAP_FUTURAMA_SEARCH_FILTER=(&(uid={{username}})(objectClass=inetOrgPerson))
+HD_AUTH_LDAP_FUTURAMA_DISPLAY_NAME_FIELD="uid"
+HD_AUTH_LDAP_FUTURAMA_USERID_FIELD="uid"
+HD_AUTH_LDAP_FUTURAMA_BIND_DN="cn=admin,dc=planetexpress,dc=com"
+HD_AUTH_LDAP_FUTURAMA_BIND_CREDENTIALS="GoodNewsEveryone"
+```
+
+You should be able to log in with either of these logins (`username` : `password`):
+
+- `professor` : `professor`
+- `fry` : `fry`
+- `zoidberg` : `zoidberg`
+- `hermes` : `hermes`
+- `leela` : `leela`
+- `bender` : `bender`
+- `amy` : `amy`
+
+If you need to know more about which information are held by each of these accounts, have a look at
+the [documentation](https://github.com/rroemhild/docker-test-openldap#ldap-structure).
+
+[docker-image]: https://github.com/rroemhild/docker-test-openldap
+[rroemhild]: https://github.com/rroemhild