Make terraform module variables nullable

[johnake]

Context

So we can have the option of leaving some parameters empty and they pick the default value or we override the default other values when we use the modules

Changes proposed in this pull request

Make terraform module variables nullable if they are optional and have default values(and the default value isn't null)

Checklist

• I have performed a self-review of my code, including formatting and typos
• I have cleaned the commit history
• I have added the Devops label
• I have attached the pull request to the trello card

[johnake]

Make terraform module variable nullable

[thomasleese]

Should we instead be setting nullable = false on the required variables? I believe nullable = true is the default for all variables.

[thomasleese]

Nice, I think there might be a few more variables where we can set nullable = false, I think pretty much any variable where there isn't a default or it's not null.