SpinApp: Support tolerations config

[vdice]

Feature request to support sending in user-defined node toleration config to the pod(s) representing a given SpinApp.

[endocrimes]

I think these would be a good fit for executor config - tolerations are things you usually want to apply to a class of software rather than one-off apps (although I'm not really sure where SpinKube would be a good fit for many of those cases - I'd love to collect some before we move ahead with design work)

[vdice]

Via executor config could work. Use case would be to isolate all SpinApps for a given executor to a subset of nodes. I don't currently envision needing finer-grained toleration/scheduling control than that.