Allow extraVolumeMounts with podSpecPatch

[bpoland]

👋 with the podSpecPatch functionality introduced in #282 I'd really like to be able to specify default volumes to mount to all containers (e.g. the extraVolumeMounts available without the patching. Is this something that could be added? Maybe an extra-volume-mounts to define in the controller helm values?

I want to use this to mount an agent hooks volume as well as pipeline signing keys. Thanks!

[moskyb]

kia ora @bpoland! this would be a useful feature to have in the k8s stack, and we'll it to our backlog. in the meantime, we would happily accept PRs to this effect. if you want to reach out to me or @DrJosh9000 on slack, we can potentially help you out with implementation stuff, if you're interested.