Restructure start script, extract provider specific scripts and add support for fetching configs from URL

openvpn/modify-openvpn-config.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+echo "Modify chosen OpenVPN config for best behaviour in this container"
+
+# Every config modification have its own environemnt variable that can configure the behaviour.
+# Different users, providers or host systems might have specific preferences.
+# But we should try to add sensible defaults, a way to disable it, and alternative implementations as needed.
+
+CONFIG_MOD_USERPASS=${CONFIG_MOD_USERPASS:-"1"}
+
+
+## Option 1 - Change the auth-user-pass line to point to credentials file
+if [[ $CONFIG_MOD_USERPASS == "1" ]]; then
+    echo "Point auth-user-pass option to the username/password file"
+    sed -i "s/auth-user-pass/auth-user-pass \/config\/openvpn-credentials.txt/" "$CHOSEN_OPENVPN_CONFIG"
+fi