Integrate with Secret Managers in Templates/Workflows

[chrisdoherty4]

We need first class construct, design, etc for secret management in HookOS, Templates and Workflows.

[chrisdoherty4]

@jacobweinstock I'm not sure what integrations you're envisaging so you might want to add some detail.

[jacobweinstock]

This might be better renamed to something like secret management in templates/workflows.