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.

CHANGELOG.md

@@ -35,6 +35,9 @@ The most noteworthy change of this release is the update of the container's base
 
 ### Updates
 
+- **Environment Variables:**
+  - `ONE_DIR` has been removed (legacy ENV) ([#3840](https://github.com/docker-mailserver/docker-mailserver/pull/3840))
+    - It's only functionality remaining was to opt-out of run-time state consolidation with `ONE_DIR=0` (_when a volume was already mounted to `/var/mail-state`_).
 - **Tests:**
   - Refactored helper methods for sending e-mails with specific `Message-ID` headers and the helpers for retrieving + filtering logs, which together help isolate logs relevant to specific mail when multiple mails have been processed within a single test. ([#3786](https://github.com/docker-mailserver/docker-mailserver/pull/3786))
 

target/scripts/startup/setup.d/mail_state.sh

@@ -7,7 +7,7 @@ function _setup_save_states() {
 
   STATEDIR='/var/mail-state'
 
-  if [[ ${ONE_DIR} -eq 1 ]] && [[ -d ${STATEDIR} ]]; then
+  if [[ -d ${STATEDIR} ]]; then
     _log 'debug' "Consolidating all state onto ${STATEDIR}"
 
     # Always enabled features:
@@ -111,9 +111,7 @@ function _setup_save_states() {
     # Ref: https://github.com/docker-mailserver/docker-mailserver/pull/3625
     chmod 730 "${STATEDIR}/spool-postfix/maildrop"
     chmod 710 "${STATEDIR}/spool-postfix/public"
-  elif [[ ${ONE_DIR} -eq 1 ]]; then
-    _log 'warn' "'ONE_DIR=1' but no volume was mounted to '${STATEDIR}'"
   else
-    _log 'debug' 'Not consolidating state (because it has been disabled)'
+    _log 'debug' "'${STATEDIR}' is not present; Not consolidating state"
   fi
 }

target/scripts/startup/variables-stack.sh

@@ -141,7 +141,6 @@ function __environment_variables_general_setup() {
   VARS[LOGWATCH_INTERVAL]="${LOGWATCH_INTERVAL:=none}"
   VARS[LOGWATCH_RECIPIENT]="${LOGWATCH_RECIPIENT:=${REPORT_RECIPIENT}}"
   VARS[LOGWATCH_SENDER]="${LOGWATCH_SENDER:=${REPORT_SENDER}}"
-  VARS[ONE_DIR]="${ONE_DIR:=1}"
   VARS[PERMIT_DOCKER]="${PERMIT_DOCKER:=none}"
   VARS[PFLOGSUMM_RECIPIENT]="${PFLOGSUMM_RECIPIENT:=${REPORT_RECIPIENT}}"
   VARS[PFLOGSUMM_SENDER]="${PFLOGSUMM_SENDER:=${REPORT_SENDER}}"