[terraform plugin] Remove stage config for TERRAFORM_APPLY

[ffjlabo]

What this PR does:

as title

Why we need it:

Currently, the TERRAFORM_APPLY stage doesn't have any options.

pipecd/pkg/app/pipedv1/plugin/terraform/config/config.go

Lines 61 to 63 in 96c15d8

	// TerraformApplyStageOptions contains all configurable values for a TERRAFORM_APPLY stage.
	type TerraformApplyStageOptions struct {
	}

So we don't need the logic for now. Also, it led the failure to execute TERRAFORM_APPLY as QuickSync

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 28.71%. Comparing base (96c15d8) to head (cf89000).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6259      +/-   ##
==========================================
+ Coverage   28.69%   28.71%   +0.01%     
==========================================
  Files         560      560              
  Lines       59738    59749      +11     
==========================================
+ Hits        17144    17159      +15     
+ Misses      41278    41271       -7     
- Partials     1316     1319       +3     

Flag	Coverage Δ
.	23.21% <ø> (-0.02%)	⬇️
.-pkg-app-pipedv1-plugin-analysis	32.64% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes	58.19% <ø> (+0.29%)	⬆️
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	67.48% <ø> (ø)
.-pkg-app-pipedv1-plugin-scriptrun	54.83% <ø> (ø)
.-pkg-app-pipedv1-plugin-terraform	39.56% <ø> (+0.30%)	⬆️
.-pkg-app-pipedv1-plugin-wait	35.51% <ø> (ø)
.-pkg-app-pipedv1-plugin-waitapproval	55.73% <ø> (ø)
.-pkg-plugin-sdk	50.47% <ø> (ø)
.-tool-actions-gh-release	19.23% <ø> (ø)
.-tool-actions-plan-preview	25.51% <ø> (ø)
.-tool-codegen-protoc-gen-auth	0.00% <ø> (ø)

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[t-kikuc]

thank you

[khanhtc1202]

@ffjlabo Should we remove the config.TerraformApplyStageOptions structure and this commented code block? If it's not being used, better to remove it 🤔

[khanhtc1202]

Also, the root cause of this issue is more like the input.Request.StageConfig is nil, so it's better to have a nil check for input.Request.StageConfig before unmarshalling, wdyt?

[ffjlabo]

@khanhtc1202
As you said, this option is not used for now. I will remove this logic and struct.

pipecd/pkg/config/application_terraform.go

Lines 60 to 73 in af58b81

	// TerraformSyncStageOptions contains all configurable values for a TERRAFORM_SYNC stage.
	type TerraformSyncStageOptions struct {
	}
	// TerraformPlanStageOptions contains all configurable values for a TERRAFORM_PLAN stage.
	type TerraformPlanStageOptions struct {
	// Exit the pipeline if the result is "No Changes" with success status.
	ExitOnNoChanges bool `json:"exitOnNoChanges"`
	}
	// TerraformApplyStageOptions contains all configurable values for a TERRAFORM_APPLY stage.
	type TerraformApplyStageOptions struct {
	}

Also, the root cause of this issue is more like the input.Request.StageConfig is nil, so it's better to have a nil check for input.Request.StageConfig before unmarshalling, wdyt?

It is good for the work around. But we might solve this problem in the piped or SDK.
But I will remove this logic.

[khanhtc1202]

Thanks, please remove the code block instead of comment out.

[khanhtc1202]

Thank you! 🙏
Note: We will make another issue for updating the SDK to ensure the stage config is not nil.