Buildpack lifecycle stack should be optional

[danail-branekov]

Background

According to the cf api docs "If a stack is not specified, then the app will default to the operator-configured default stack", meaning that the lifecycle stack should be optional

Acceptance

WHEN I create an app via the floowing request

curl "https://api.example.org/v3/apps" \
  -X POST \
  -H "Authorization: bearer [token]" \
  -H "Content-type: application/json" \
  -d '{
    "name": "my_app",
    "relationships": {
      "space": {
        "data": {
          "guid": "2f35885d-0c9d-4423-83ad-fd05066f8576"
        }
      }
    },
    "lifecycle": {
      "type": "buildpack",
    }
  }'

THEN I see the request succeed and I get a response saying that the stack has been defaulted

HTTP/1.1 201 Created
Content-Type: application/json

{
  "guid": "1cb006ee-fb05-47e1-b541-c34179ddc446",
  "name": "my_app",
  "state": "STOPPED",
  "created_at": "2016-03-17T21:41:30Z",
  "updated_at": "2016-06-08T16:41:26Z",
  "lifecycle": {
    "type": "buildpack",
    "data": {
      "stack": "cflinuxfs4"
    }
  },
  "relationships": {
    "space": {
      "data": {
        "guid": "2f35885d-0c9d-4423-83ad-fd05066f8576"
      }
    }
  }
}

Dev notes

We should basically get rid of this method:

korifi/api/payloads/lifecycle.go

Lines 25 to 29 in e9067c8

	func (d LifecycleData) Validate() error {
	return jellidation.ValidateStruct(&d,
	jellidation.Field(&d.Stack, jellidation.Required),
	)
	}