feat: Add setHeader functionality for httpRoutes

[Philipp-Plotnikov]

Example of ArgoRollouts

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: rollouts-demo
spec:
  replicas: 4
  revisionHistoryLimit: 2
  selector:
    matchLabels:
      app: rollouts-demo
  template:
    metadata:
      labels:
        app: rollouts-demo
    spec:
      containers:
      - name: rollouts-demo
        image: argoproj/rollouts-demo:orange
        ports:
        - name: http
          containerPort: 8080
          protocol: TCP
  strategy:
    canary:
      stableService: stable-service
      canaryService: canary-service
      trafficRouting:
        managedRoutes:
          - name: header-route
        plugins:
          argoproj-labs/gatewayAPI:
            namespace: default                                                                                                
            httpRoute: http-route
            configMap: test-gateway
      steps:
      - setWeight: 20
      - pause: {duration: 10}
      - setWeight: 40
      - pause: {duration: 20}
      - setWeight: 60
      - setHeaderRoute:
          name: header-route
          match:
            - headerName: X-Test
              headerValue:
                exact: test
      - pause: {duration: 5}
      - setWeight: 80
      - setHeaderRoute: # remove header route
          name: header-route
      - pause: {}

Plugin will take "http-route" of HttpRoute type and will add rules corresponding setHeaderRoute step. One step - one rule. Also it will add Path and QueryParams match from first HTTPRoute rule where stable and canary service is. GatewayAPI will use rule where more matches fit. Plugin will delete header rules when it will get event removeManagedRoutes or on the step like in the example (remove header route)

apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: http-route
spec:
  parentRefs:
    - name: argo-gateway
      sectionName: http
  rules:
    - backendRefs:
      - name: stable-service
        port: 80
        weight: 100
      - name: canary-service
        port: 80
      matches:
      - path:
           type: PathPrefix
           value: /test

After setHeaderRoute step

apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: http-route
spec:
  parentRefs:
    - name: argo-gateway
      sectionName: http
  rules:
    - backendRefs:
      - name: stable-service
        port: 80
        weight: 100
      - name: canary-service
        port: 80
      matches:
      - path:
           type: PathPrefix
           value: /
    - backendRefs:                                                                                                              
       - group: ""                                                                                                               
          kind: Service                                                                                                           
          name: canary-service                                                                                                    
          port: 80                                                                                                                
         weight: 1                                                                                                               
      matches:                                                                                                                  
       - headers:                                                                                                                
         - name: X-Test                                                                                                          
            type: Exact                                                                                                           
            value: test                                                                                                           
        path:                                                                                                                   
          type: PathPrefix                                                                                                      
          value: /test

Plugin save where(which index) and what headerRoute step in configMap. Plugin creates if configMap wasn't created with specified name under key configMap and in specified namespace under key namespace like here

apiVersion: v1
kind: ConfigMap
metadata:
  name: test-gateway
  namespace: default
data:
   httpManagedRoutes: '{"header-route": 1}'

If you dont specify the configMap, its default name will be argo-gatewayapi-configmap