[CSGI-2172 ] Support for Intelligent Time Window to Alert Grouping Parameters

[imjaroiswebdev]

Add support for Intelligent Time Window to Service Alert Grouping Parameters configuration, allowing from this point to do the following...

resource "pagerduty_service" "example" {
  name                    = "My Web App"
  auto_resolve_timeout    = 14400
  acknowledgement_timeout = 600
  escalation_policy       = pagerduty_escalation_policy.foo.id
  alert_creation          = "create_alerts_and_incidents"

  auto_pause_notifications_parameters {
    enabled = true
    timeout = 300
  }
  alert_grouping_parameters {
    type = "intelligent"
    config {
      time_window = 300 # 👈 New attribute introduced
    }
  }
}

Additionally, validation for Alert Grouping Parameters configuration options was introduced, producing the following output based on the type of alert grouping set...

│ Error: Alert grouping parameters configuration of type "intelligent" only supports setting the optional attribute "time_window"
│

│ Error: Alert grouping parameters configuration of type "content_based" only supports setting "aggregate" and "fields" attributes
│

│ Error: Alert grouping parameters configuration of type "time" only supports setting "timeout" attribute
│

New test cases introduced...

$ make testacc TESTARGS="-run TestAccPagerDutyService_AlertContentGroupingIntelligentTimeWindow"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test $(go list ./... |grep -v 'vendor') -v -run TestAccPagerDutyService_AlertContentGroupingIntelligentTimeWindow -timeout 120m
?       github.com/terraform-providers/terraform-provider-pagerduty     [no test files]
=== RUN   TestAccPagerDutyService_AlertContentGroupingIntelligentTimeWindow
--- PASS: TestAccPagerDutyService_AlertContentGroupingIntelligentTimeWindow (18.30s)
PASS
ok      github.com/terraform-providers/terraform-provider-pagerduty/pagerduty   18.822s

Depends on heimweh/go-pagerduty#142