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/create_ssl_certs.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+postgres_service_dir="$1"
+
+cd "$postgres_service_dir"
+mkdir certs && cd certs
+openssl req -new -newkey rsa:4096 -x509 -days 365000 -nodes -out server.crt -keyout server.key -batch