Add imagePullSecrets support to rancher-webhook.

[frank-m]

Problem

rancher-webhook does not support imagepullsecrets. When using private registries this can be very annoying as the main rancher chart does support them, but subsequent pulls will fail.

Solution

Added some yaml templating and tests to add imagepullsecrets. Also added default value.

CheckList

• Test
• Docs

[tomleb]

Hi @frank-m, first thanks for the contribution.

There's an on-going effort to add support for imagePullSecrets to a few other rancher components lead by another team so I believe we'll need this eventually, just not sure yet if as is fine or will need changes. Let me do some digging on that effort.