The name of the workspace template to base the workspace on: resolved
at creation time to whatever template currently carries that name
(convenience reference; set template_id instead to pin an exact
template). Applied only when creating a new workspace: the template is
resolved to a snapshot of its values at creation time, so later
template edits affect only newly created workspaces. On create,
conflicts with spec: set either template fields or explicit parameters,
never both. When upserting an existing workspace, spec may accompany an
echo-equal template reference: a read-modify-write round trip carries
both, and divergent values are rejected. Set at most
one of template_name/template_id on input; when both are set they must
refer to the same template. Immutable after creation: when upserting
an existing workspace, must be absent or equal to the stored value.
After creation, always populated together with template_id as a
historical record; template edits or deletion do not affect the
workspace.