Allow addtional flags and environment variables for Terraform plan-preview

[kentakozuka]

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes # #2840

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

Failed while validating Kapetanios configuration.

Details

Error: rpc error: code = NotFound desc = not found

[pipecd-bot]

Welcome @kentakozuka!

Thanks for your contributing. It looks like this is your first PR to this repository 🎉. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA). Please read the CLA and leave a /cla sign comment on this pull request to sign the CLA.

[kentakozuka]

/cla sign

[pipecd-bot]

Thank you for signing the CLA. Your signing has been successfully committed.

[pipecd-bot]

Code coverage for golang is 31.73%. This pull request decreases coverage by -0.12%.

File	Function	Base	Head	Diff
pkg/app/api/grpcapi/piped_api.go	PipedAPI.InChainDeploymentPlannable	--	0.00%	+0.00%
pkg/app/piped/cloudprovider/kubernetes/state.go	determineNameSpace	--	0.00%	+0.00%
pkg/config/config.go	Kind.ToApplicationKind	--	100.00%	+100.00%
pkg/datastore/deploymentchainstore.go	deploymentChainStore.UpdateDeploymentChain	--	0.00%	+0.00%
pkg/datastore/deploymentchainstore.go	deploymentChainStore.GetDeploymentChain	--	0.00%	+0.00%
pkg/model/deployment.go	IsSuccessfullyCompletedDeployment	--	0.00%	+0.00%
pkg/app/piped/trigger/trigger.go	Trigger.checkRepoCandidates	0.00%	0.00%	+0.00%
pkg/app/api/grpcapi/piped_api.go	PipedAPI.CreateDeployment	0.00%	0.00%	+0.00%
pkg/app/piped/appconfigreporter/appconfigreporter.go	Reporter.readApplicationInfo	75.00%	73.33%	-1.67%
pkg/app/piped/cloudprovider/kubernetes/state.go	determineResourceHealth	0.00%	0.00%	+0.00%
pkg/app/piped/planpreview/terraformdiff.go	builder.terraformDiff	0.00%	0.00%	+0.00%

[nghialv]

Nice catch! Thank you.
/lgtm

[ono-max]

/approve

[pipecd-bot]

This pull request is APPROVED by ono-max.

Approvers can cancel the approval by writing /approve cancel in a comment. Any additional commits also will change this pull request to be not-approved.