fix: create ssl certs outside container

This enables support for alpine-based images like timescaledb (no bash/openssl).

Fixes #153
Fixes timescale/timescaledb-docker#99

scripts/enable_ssl.sh

@@ -1,7 +1,10 @@
-#!/bin/bash
-pushd /var/lib/postgresql/data >/dev/null
-openssl req -new -newkey rsa:4096 -x509 -days 365000 -nodes -out server.crt -keyout server.key -batch
+#!/bin/sh
+
+cd /var/lib/postgresql/data
+
+cp ../certs/* .
+chown postgres:postgres server.key
 chmod 600 server.key
+
 sed -i "s/^#ssl = off/ssl = on/" postgresql.conf
 sed -i "s/^#ssl_ciphers =.*/ssl_ciphers = 'AES256+EECDH:AES256+EDH'/" postgresql.conf
-popd >/dev/null