Make service destination protocol and ports configurable

The current implementation in prepare.sh is hard coded with tcp and ports 20 through 10000. Pulling this up to be configurable in main.tf would be a nice first step. I am unsure if allowing configuration in .gitlab-ci.yml at run time is worth the lift and considering the ability to modify it with the code, is probably less secure.

Considerations:

• Deploy-time option
• Configurable in Gitlab CI yaml