[FEATURE] Workflow Instantiation - GET template endpoint

**Is your feature request related to a problem? Please describe.**
User is creating CI/CD for workflows and components.

**Describe the solution you'd like**
Request is to be able to get a workflow's template via API (e.g. `tch_id`, payload)

**Do you have a workaround?**
Have to "Instantiate via API" from workflow builder.

**Comparable features in other tools?**
n/a

**Additional context**