[1.14] Expose most_specific_header_mutations wins and use append_action

[inFocus7]

backport of #8678 + #8692

Description

API/Code changes

• Exposed the most_specific_header_mutation_wins in RouteConfigurations.
• Add RouteTableOptions to TestContext's TestClients
• Add tests for most_specific_header_mutations_wins
• append translates to Envoy's append_action
  • append: true => append_action: APPEND_IF_EXISTS_OR_ADD
  • append: false => append_action: OVERWRITE_IF_EXISTS_OR_ADD

Docs changes

• Update header manipulation docs information.
• Add section in header manipulation docs bringing up this flag and its behavior

Context

• Users want a way to prioritize the mutation done by a route, instead of one done by a vhost.

Testing steps

./ci/kind/setup-kind.sh

helm install gloo _test/gloo-1.0.0-ci.tgz

kubectl apply -f - << 'EOF' 
apiVersion: v1
kind: ServiceAccount
metadata:
  name: httpbin
---
apiVersion: v1
kind: Service
metadata:
  name: httpbin
  labels:
    app: httpbin
spec:
  type: ClusterIP
  ports:
  - name: http
    port: 80
    targetPort: 80
  selector:
    app: httpbin
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpbin
spec:
  replicas: 1
  selector:
    matchLabels:
      app: httpbin
      version: v1
  template:
    metadata:
      labels:
        app: httpbin
        version: v1
    spec:
      serviceAccountName: httpbin
      containers:
      - image: docker.io/kennethreitz/httpbin
        imagePullPolicy: IfNotPresent
        name: httpbin
        ports:
        - containerPort: 80
EOF

kubectl apply -f - << 'EOF'
apiVersion: gateway.solo.io/v1
kind: VirtualService
metadata:
  name: default
  namespace: default
spec:
  virtualHost:
    domains:
    - '*'
    options:
      headerManipulation:
        responseHeadersToAdd:
        - header:
           key: X-Frame-Options
           value: VSORIGIN
          append: false
    routes:
    - delegateAction:
        selector:
          labels:
            delegate: 'true'
      matchers:
      - prefix: /
EOF

kubectl apply -f - << 'EOF'
apiVersion: gateway.solo.io/v1
kind: RouteTable
metadata:
  labels:
    delegate: 'true'
  name: child
  namespace: default
spec:
  routes:
  - matchers:
    - prefix: /get
    options:
      headerManipulation:
        responseHeadersToAdd:
        - header:
            key: X-Frame-Options
            value: RTORIGIN
          append: false
    routeAction:
      single:
        upstream:
          name: default-httpbin-80
          namespace: default
EOF

kubectl port-forward -n gloo-system deploy/gateway-proxy 8080:8080 & proxynormalPortFwdPid=$!

curl http://localhost:8080/get -v

Notice only the VS header (VSORIGIN) is in the header x-frame-options. This is because we have append: false on the header, therefore it is set to overwrite any headers that came before.

Edit the gateway resource to include spec.routeOptions.mostSpecificHeaderMutationsWins: true field.

curl http://localhost:8080/get -v

Notice that now, only the Route header (RTORIGIN) is in the header x-frame-options. This is because our route config is now set to prioritize the most specific header mutation.

Notes for reviewers

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[solo-changelog-bot]

Issues linked to changelog:
#8525
#8690

[inFocus7]

FIX, as it's a backport so we can't use NEW_FEATURE, but want this change to be visible to users.