Re-design ServiceExpose trait

[resouer]

The idea is Expose should answer below questions:

1. which target port I want to expose?
2. expose to what service port?
3. what's the type of this expose?
4. what's the protocol?

It should be a list, with Kind of Expose. So I'd suggest re-design ServiceExpose as below.

Example 1:

apiVersion: core.oam.dev/v1alpha2
kind: Expose
spec:
  servicePorts:
    - port: 80
      targetPort: 80
    - port: 8001
      targetPort: 9376

This will generate one k8s Service:

apiVersion: v1
kind: Service
metadata:
  name: <component-name>-clusterip
spec:
  clusterIP: 10.96.193.247 # auto gen
  ports:
  - name: tcp-80 # auto gen
    port: 80
    protocol: TCP # default
    targetPort: 80
  - name: tcp-8080 # auto-gen
    port: 8080
    protocol: TCP # default
    targetPort: 80
  selector:
    component: <component-name>
  type: ClusterIP

Example 2:

apiVersion: core.oam.dev/v1alpha2
kind: Expose
spec:
  servicePorts:
    - port: 80
      targetPort: 80
      type: NodePort
    - port: 8001
      targetPort: 9376
      clusterIP: 10.0.171.239
      type: LoadBalancer
      protocol: HTTP

This will generate two k8s Services:

apiVersion: v1
kind: Service
metadata:
  name: <component-name>-nodeport
spec:
  type: NodePort
  ports:
  - name: tcp-80 # auto gen
    port: 80
    protocol: TCP # default
    targetPort: 80
  selector:
    component: <component-name> # this is auto label for workload

apiVersion: v1
kind: Service
metadata:
  name: <component-name>-loadbalancer
spec:
  type: LoadBalancer
  clusterIP: 10.0.171.239
  ports:
  - name: http-8001 # auto gen
    port: 8001
    protocol: HTTP
    targetPort: 9376
  selector:
    component: <component-name> # this is auto label for workload

For auto labels of workload, ref: crossplane/oam-kubernetes-runtime#174

[resouer]

/cc @wonderflow

[hongchaodeng]

I would recommend to take a look at the port abstraction in Exposing the service section in this blog: https://medium.com/kapitan-blog/keep-your-ship-together-with-kapitan-d82d441cc3e7