Add deploy hook for mailcow

This hook will copy the key and certificate chain to the specified
mailcow installation (as described in
https://mailcow.github.io/mailcow-dockerized-docs/firststeps-ssl/#use-own-certificates)
and restarts the containers, that are using the certificates.

The hook has 2 parameters:

* `DEPLOY_MAILCOW_PATH`: The path to the mailcow installation (required)
* `DEPLOY_MAILCOW_RELOAD`: The reload command, defaults to `docker-compose restart postfix-mailcow dovecot-mailcow nginx-mailcow`

deploy/mailcow.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env sh
+
+#Here is a script to deploy cert to mailcow.
+
+#returns 0 means success, otherwise error.
+
+########  Public functions #####################
+
+#domain keyfile certfile cafile fullchain
+mailcow_deploy() {
+  _cdomain="$1"
+  _ckey="$2"
+  _ccert="$3"
+  _cca="$4"
+  _cfullchain="$5"
+
+  _debug _cdomain "$_cdomain"
+  _debug _ckey "$_ckey"
+  _debug _ccert "$_ccert"
+  _debug _cca "$_cca"
+  _debug _cfullchain "$_cfullchain"
+
+  _ssl_path="${DEPLOY_MAILCOW_PATH}/data/assets/ssl/"
+  if [ ! -d "$_ssl_path"; ] then
+      _err "Cannot find mailcow ssl path: $_ssl_path"
+      return 1
+  fi
+
+  _info "Copying key and cert"
+  _real_key="$_ssl_path/key.pem"
+  if ! cat "$_ckey" >"$_real_key"; then
+    _err "Error: write key file to: $_real_key"
+    return 1
+  fi
+
+  _real_fullchain="$_ssl_path/cert.pem"
+  if ! cat "$_cfullchain" >"$_real_fullchain"; then
+    _err "Error: write cert file to: $_real_fullchain"
+    return 1
+  fi
+
+  DEFAULT_MAILCOW_RELOAD="docker-compose restart postfix-mailcow dovecot-mailcow nginx-mailcow"
+  _reload="${DEPLOY_MAILCOW_RELOAD:-$DEFAULT_MAILCOW_RELOAD}"
+
+  _info "Run reload: $_reload"
+  if eval "$_reload"; then
+    _info "Reload success!"
+  fi
+  return 0
+
+}