Fix #2202

[titilambert]

Description

This patch allows namespaced ambassador to get K8s secrets in an other namespace.

If you want to accept this PR, I will create an other for master

Related Issues

• Ambassador isn't loading a secret in a separate namespace #2202

Testing

I deployed a namespaced ambassador, and I just added AMBASSADOR_CERTS_SINGLE_NAMESPACE env var with empty value.

        - name: AMBASSADOR_SINGLE_NAMESPACE
          value: "YES"
        - name: AMBASSADOR_CERTS_SINGLE_NAMESPACE
        - name: AMBASSADOR_NAMESPACE
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: metadata.namespace

Then in my TLScontext I'm able the set a certificate from an other namespace. (the service account of ambassador has a rolebinding allowing reading secret in the other namespace)

Todos

• Tests
• Documentation

Other

• If this is a documentation change, please open the pull request at https://github.com/datawire/ambassador-docs instead.
• Code changes should occur against master.

[kflynn]

Superseded by #2239, since this was targeted against release/0.86.1 and we won't be doing any more 0.86 releases. Thanks!!