[Stage Plugins] Define Notifier APIs of Approved and WaitApproval

[t-kikuc]

What this PR does:

as title

Why we need it:

The WaitApproval plugin needs to:

• notify approvers when the stage starts (NotificationEventDeploymentWaitApproval)
• notify when approval is completed (NotificationEventDeploymentApproved)

cf.

pipecd/pkg/app/piped/executor/waitapproval/waitapproval.go

Lines 112 to 143 in 2ce020e

	func (e *Executor) reportApproved(approver string) {
	users, groups, err := e.getApplicationNotificationMentions(model.NotificationEventType_EVENT_DEPLOYMENT_APPROVED)
	if err != nil {
	e.Logger.Error("failed to get the list of users or groups", zap.Error(err))
	}
	e.Notifier.Notify(model.NotificationEvent{
	Type: model.NotificationEventType_EVENT_DEPLOYMENT_APPROVED,
	Metadata: &model.NotificationEventDeploymentApproved{
	Deployment: e.Deployment,
	Approver: approver,
	MentionedAccounts: users,
	MentionedGroups: groups,
	},
	})
	}
	func (e *Executor) reportRequiringApproval() {
	users, groups, err := e.getApplicationNotificationMentions(model.NotificationEventType_EVENT_DEPLOYMENT_WAIT_APPROVAL)
	if err != nil {
	e.Logger.Error("failed to get the list of users or groups", zap.Error(err))
	}
	e.Notifier.Notify(model.NotificationEvent{
	Type: model.NotificationEventType_EVENT_DEPLOYMENT_WAIT_APPROVAL,
	Metadata: &model.NotificationEventDeploymentWaitApproval{
	Deployment: e.Deployment,
	MentionedAccounts: users,
	MentionedGroups: groups,
	},
	})
	}

They depend on the current matcher/sender configs.

Note

• Other notifications must NOT be triggered by plugins (e.g. DeploymentStarted, StageFinished)

• If a plugin wants to send other customized notifications, the plugin should do so within the plugin without the pipedservice.

• These pipedservice methods can be used by other plugins

  • e.g. customized notification plugin
  • The advantage of using them over full-scratch notifications is that the current matcher/sender can be used.

Which issue(s) this PR fixes:

Part of #5367

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 26.44%. Comparing base (4411ffb) to head (1fe8a7d).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5538   +/-   ##
=======================================
  Coverage   26.43%   26.44%           
=======================================
  Files         465      465           
  Lines       49858    49858           
=======================================
+ Hits        13182    13186    +4     
+ Misses      35621    35618    -3     
+ Partials     1055     1054    -1     

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