test: update Terraform test matrix

[lechnerc77]

Purpose

• Update test matrix for supported Terraform versions
• Update issue template
• Align formatting of workflow file and removed unused code
• Closes [BUG] Test matrix - Current Terraform versions missing #150

Does this introduce a breaking change?

• Yes
• No

Pull Request Type

What kind of change does this Pull Request introduce?

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Documentation content changes
• Other... Please describe: Test Setup for Terraform

How to Test

• Test the code via automated test

go test ./...

What to Check

Verify that the following are valid:

• Automated tests are executed successfully

Other Information

n/a

Checklist for reviewer

The following organizational tasks must be completed before merging this PR:

• The PR is assigned to the Terraform project and a status is set (typically "in review").
• The PR has the matching labels assigned to it.
• The PR has a milestone assigned to it.
• If the PR closes an issue, the issue is referenced.
• Possible follow-up items are created and linked.

[lechnerc77]

The mandatory checks in the repository settings must be adjusted, as some tests have been removed, but new tests have been added

[Dray56]

fixed by #167