test: add Terratest tests for managed-identity module #3482

Job	Run time
Set CI/CD metadata	5s
Commit stage / Scan dependencies	4s
Commit stage / Count lines of code	11s
Commit stage / Scan secrets	6s
Commit stage / Check file format	7s
Commit stage / Lint Terraform	5s
Test stage / Unit test terraform modules	53s
Test stage / Perform static analysis	4s
Test stage / Terraform lint (tflint)	9s
Test stage / Terraform security scan	18s
Build stage	0s
Acceptance stage	0s
	2m 2s

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