Adding OnlyOffice compose

This PR adds a compose.onlyoffice.yaml file and the corresponding
configuration and description in README.md.

onlyoffice-entrypoint.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+set -e
+
+# OnlyOffice init — runs before the original CryptPad entrypoint.
+# Ensures oldest_needed_version in onlyoffice.properties matches
+# ONLYOFFICE_OLDEST before install-onlyoffice.sh / CryptPad reads it.
+
+CONF_DIR="/cryptpad/onlyoffice-conf"
+PROPS="${CONF_DIR}/onlyoffice.properties"
+
+# Wait for init-onlyoffice-dirs to chown the volumes. Swarm ignores
+# depends_on, so the init sidecar and this container start in parallel.
+waited=0
+while [ ! -w "${CONF_DIR}" ]; do
+  if [ "${waited}" -ge 60 ]; then
+    echo "[onlyoffice-entrypoint] timed out waiting for ${CONF_DIR} to become writable" >&2
+    exit 1
+  fi
+  echo "[onlyoffice-entrypoint] waiting for ${CONF_DIR} to be writable (${waited}s)"
+  sleep 1
+  waited=$((waited + 1))
+done
+
+if [ -n "${ONLYOFFICE_OLDEST:-}" ]; then
+  mkdir -p "${CONF_DIR}"
+  touch "${PROPS}"
+  if grep -q '^oldest_needed_version=' "${PROPS}"; then
+    sed -i "s|^oldest_needed_version=.*|oldest_needed_version=${ONLYOFFICE_OLDEST}|" "${PROPS}"
+  else
+    echo "oldest_needed_version=${ONLYOFFICE_OLDEST}" >> "${PROPS}"
+  fi
+  echo "[onlyoffice-entrypoint] oldest_needed_version=${ONLYOFFICE_OLDEST}"
+else
+  echo "[onlyoffice-entrypoint] ONLYOFFICE_OLDEST unset, leaving ${PROPS} untouched"
+fi
+
+# Chain through the SSO entrypoint if compose.sso.yml mounted it.
+if [ -x /sso-entrypoint.sh ]; then
+  exec /sso-entrypoint.sh "$@"
+fi
+
+exec "$@"