* Replace v0.11 bracket type hints with Terraform v0.12 list expressions
* Use expression syntax instead of interpolated strings, where suggested
* Update Azure tutorial and worker pools documentation
* Define Terraform and plugin version requirements in versions.tf
* Require azurerm ~> 1.27 to support Terraform v0.12
* Require ct ~> 0.3.2 to support Terraform v0.12