Merge #2101

2101: Fix documentation  INITIAL_ADMIN_* variables r=mergify[bot] a=Erriez

## What type of PR?

Fix `master` documentation `INITIAL_ADMIN_*` environment variables:
- `setup.rst`
- `configuration.rst`

## What does this PR do?

Fix documentation `Docker Compose setup` and `Web settings | Admin account`.

### Related issue(s)
- Mention an issue like: #2092
- Auto close an issue like: closes #2092

## Prerequisites
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [X] In case of feature or enhancement: documentation updated accordingly
- [ ] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/workflow.html#changelog) entry file.


Co-authored-by: Erriez <Erriez@users.noreply.github.com>

docs/compose/setup.rst

@@ -99,8 +99,7 @@ You may now start Mailu. Move the to the Mailu directory and run:
 Finally, you need an admin user account. 
 
 You can have the system create it automatically:
-use the environment variables ``INITIAL_ACCOUNT*`` as described in :ref:`admin_account`
-You should set ``INITIAL_ADMIN_MODE`` also to either ``update`` or ``ifmissing``. Leaving it with the default value could cause errors when restarting the system.  
+use the environment variables ``INITIAL_ADMIN_*`` as described in :ref:`admin_account`
 
 Else, if you don't go with the automatic way, you need to manually create the admin account now:
 

docs/configuration.rst

@@ -159,18 +159,25 @@ To create it manually, follow the specific deployment method documentation.
 
 To have the account created automatically, you just need to define a few environment variables:
 
+- ``INITIAL_ADMIN_ACCOUNT``: the admin username: The first part of the e-mail address before the @.
+- ``INITIAL_ADMIN_DOMAIN``: the domain appendix: Most probably identical to the ``DOMAIN`` variable.
+- ``INITIAL_ADMIN_PW``: the admin password.
+- ``INITIAL_ADMIN_MODE``: use one of the options below for configuring how the admin account must be created:
+  
+  - ``create``: (default) creates a new admin account and raises an exception when it already exists.
+  - ``ifmissing``: creates a new admin account when the admin account does not exist.
+  - ``update``: creates a new admin account when it does not exist, or update the password of an existing admin account.
+
+Note: It is recommended to set ``INITIAL_ADMIN_MODE`` to either ``update`` or ``ifmissing``. Leaving it with the default value will cause an error when the system is restarted.
+
+An example:
+
 .. code-block:: bash
 
-  INITIAL_ADMIN_ACCOUNT = ``root`` The first part of the e-mail address (ROOT@example.com)
-  INITIAL_ADMIN_DOMAIN = ``example.com`` the domain appendix. Most probably identical to the DOMAIN variable
-  INITIAL_ADMIN_PW = ``password`` the chosen password for the user
-
-Also, environment variable ``INITIAL_ADMIN_MODE`` defines how the code should behave when it will
-try to create the admin user:
-
-- ``create`` (default) Will try to create user and will raise an exception if present
-- ``ifmissing``: if user exists, nothing happens, else it will be created
-- ``update``: user is created or, if it exists, its password gets updated
+  INITIAL_ADMIN_ACCOUNT=me
+  INITIAL_ADMIN_DOMAIN=example.net
+  INITIAL_ADMIN_PW=password
+  INITIAL_ADMIN_MODE=ifmissing
 
 Depending on your particular deployment you most probably will want to change the default.