fix(mongodbflex): instance unit tests failing

[j1n-o9r]

Description

Unit tests are failing with SDK mongodbflex v1.9.0 or above.

➜  terraform-provider-stackit git:(fix/STACKITTPR-677-mongodbflex-instance-unit-tests-failing) ✗ go test ./stackit/internal/services/mongodbflex/instance/
# github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/mongodbflex/instance [github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/mongodbflex/instance.test]
stackit/internal/services/mongodbflex/instance/resource_test.go:125:16: cannot use new("READY") (value of type *string) as *v2api.InstanceStatus value in struct literal
stackit/internal/services/mongodbflex/instance/resource_test.go:200:22: cannot use new("READY") (value of type *string) as *v2api.InstanceStatus value in struct literal
stackit/internal/services/mongodbflex/instance/resource_test.go:285:22: cannot use new("READY") (value of type *string) as *v2api.InstanceStatus value in struct literal
FAIL    github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/mongodbflex/instance [build failed]
FAIL

relates to STACKITTPR-677

Checklist

• Issue was linked above
• Code format was applied: make fmt
• Examples were added / adjusted (see examples/ directory)
• Docs are up-to-date: make generate-docs (will be checked by CI)
• Unit tests got implemented or updated
• Acceptance tests got implemented or updated (see e.g. here)
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

[github-actions]

Merging this branch will not change overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/mongodbflex/instance	29.48% (ø)

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Coverage by file

Changed unit test files

• github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/mongodbflex/instance/resource_test.go