docs: Remove ENV ONE_DIR (#3840)

* docs: Better document DMS volumes

* docs: Remove any mention of `ONE_DIR` ENV

* chore: Remove `ONE_DIR` ENV from scripts

Only `ONE_DIR=0` has any effect. As the actual feature is now dependent upon the `/var/mail-state` location existing.

It is advised not mounting anything there instead if wanting to avoid runtime state consolidation.

* docs: Adjust link ref convention

This is more search friendly / organized to find references to all DMS volumes.

* lint: Ensure final newline is present

VSCode by default excludes this if the last line rendered is removed (rendered as a separate blank line).

A separate setting can enforce adding the final newline upon save regardless.

docs/content/config/advanced/kubernetes.md

@@ -40,7 +40,6 @@ data:
   POSTMASTER_ADDRESS: postmaster@example.com
   UPDATE_CHECK_INTERVAL: 10d
   POSTFIX_INET_PROTOCOLS: ipv4
-  ONE_DIR: '1'
   ENABLE_CLAMAV: '1'
   ENABLE_POSTGREY: '0'
   ENABLE_FAIL2BAN: '1'

docs/content/config/advanced/optional-config.md

@@ -4,9 +4,64 @@ hide:
   - toc # Hide Table of Contents for this page
 ---
 
-This is a list of all configuration files and directories which are optional or automatically generated in your [`docker-data/dms/config/`][docs-dms-config-volume] directory.
+## Volumes
 
-## Directories
+DMS has several locations in the container which may be worth persisting externally via [Docker Volumes][docker-docs::volumes].
+
+- Often you will want to prefer [bind mount volumes][docker-docs::volumes::bind-mount] for easy access to files at a local location on your filesystem.
+- As a convention for our docs and example configs, the local location has the common prefix `docker-data/dms/` for grouping these related volumes.
+
+!!! info "Reference - Volmes for DMS"
+
+    Our docs may refer to these DMS specific volumes only by name, or the host/container path for brevity.
+
+    - [Config](#volumes-config): `docker-data/dms/config/` => `/tmp/docker-mailserver/`
+    - [Mail Storage](#volumes-mail): `docker-data/dms/mail-data/` => `/var/mail/`
+    - [State](#volumes-state): `docker-data/dms/mail-state/` => `/var/mail-state/`
+    - [Logs](#volumes-logs): `docker-data/dms/mail-logs/` => `/var/log/mail/`
+
+[docker-docs::volumes]: https://docs.docker.com/storage/volumes/
+[docker-docs::volumes::bind-mount]: https://docs.docker.com/storage/bind-mounts/
+
+### Mail Storage Volume { #volumes-mail }
+
+This is the location where mail is delivered to your mailboxes.
+
+### State Volume { #volumes-state }
+
+Run-time specific state lives here, but so does some data you may want to keep if a failure event occurs (_crash, power loss_).
+
+!!! example "Examples of relevant data"
+
+    - The Postfix queue (eg: mail pending delivery attempt)
+    - Fail2Ban blocks.
+    - ClamAV signature updates.
+    - Redis storage for Rspamd.
+
+!!! info "When a volume is mounted to `/var/mail-state/`"
+
+    - Service run-time data is [consolidated into the `/var/mail-state/` directory][mail-state-folders]. Otherwise the original locations vary and would need to be mounted individually.
+    - The original locations are updated with symlinks to redirect to their new path in `/var/mail-state/` (_eg: `/var/lib/redis` => `/var/mail-state/lib-redis/`_).
+
+    Supported services: Postfix, Dovecot, Fail2Ban, Amavis, PostGrey, ClamAV, SpamAssassin, Rspamd & Redis, Fetchmail, Getmail, LogRotate, PostSRSd, MTA-STS.
+
+!!! tip
+
+    Sometimes it is helpful to disable this volume when troubleshooting to verify if the data stored here is in a bad state (_eg: caused by a failure event_).
+
+[mail-state-folders]: https://github.com/docker-mailserver/docker-mailserver/blob/v13.3.1/target/scripts/startup/setup.d/mail_state.sh#L13-L33
+
+### Logs Volume { #volumes-log }
+
+This can be a useful volume to persist for troubleshooting needs for the full set of log files.
+
+### Config Volume { #volumes-config }
+
+Most configuration files for Postfix, Dovecot, etc. are persisted here.
+
+This is a list of all configuration files and directories which are optional, automatically generated / updated by our `setup` CLI, or other internal scripts.
+
+#### Directories
 
 - **sieve-filter:** directory for sieve filter scripts. (Docs: [Sieve][docs-sieve])
 - **sieve-pipe:** directory for sieve pipe scripts. (Docs: [Sieve][docs-sieve])
@@ -14,7 +69,7 @@ This is a list of all configuration files and directories which are optional or
 - **ssl:** SSL Certificate directory if `SSL_TYPE` is set to `self-signed` or `custom`. (Docs: [SSL][docs-ssl])
 - **rspamd:** Override directory for custom settings when using Rspamd (Docs: [Rspamd][docs-rspamd-override-d])
 
-## Files
+#### Files
 
 - **{user_email_address}.dovecot.sieve:** User specific Sieve filter file. (Docs: [Sieve][docs-sieve])
 - **before.dovecot.sieve:** Global Sieve filter file, applied prior to the `${login}.dovecot.sieve` filter. (Docs: [Sieve][docs-sieve])
@@ -42,7 +97,6 @@ This is a list of all configuration files and directories which are optional or
 - **user-patches.sh:** this file will be run after all configuration files are set up, but before the postfix, amavis and other daemons are started. (Docs: [FAQ - How to adjust settings with the `user-patches.sh` script][docs-faq-userpatches])
 - **rspamd/custom-commands.conf:** list of simple commands to adjust Rspamd modules in an easy way (Docs: [Rspamd][docs-rspamd-commands])
 
-[docs-dms-config-volume]: ../../faq.md#what-about-the-docker-datadmsconfig-directory
 [docs-accounts-quota]: ../../config/user-management.md#quotas
 [docs-aliases-regex]: ../../config/user-management.md#configuring-regexp-aliases
 [docs-dkim]: ../../config/best-practices/dkim_dmarc_spf.md#dkim