Which workspace a template is in, for a link that names no workspace

For an old link (`/sign/templates/<id>/use`, an email from before workspace URLs), so the app can send the tab to the same route under `/w/<slug>`. It works across the caller's workspaces: the token may be for any of them. It answers only when the caller could open the template in its own workspace: they are a member with a product seat, Sign is on there, and the template is theirs or shared with the workspace. Built-in templates open in any workspace and are not located. Rows from before workspaces (no workspace) are not located. Every other case gets the same 404, byte for byte: no such template, someone else's private one, another workspace's, the product turned off there, a malformed id, or a request made with an API key or an OAuth grant (those are bound to one workspace by consent). Both answers are `Cache-Control: no-store`. Rate-limited per user and per client IP.

curl -X GET "https://example.com/v1/templates/string/locate"

{  "workspace_id": "0967198e-ec7b-4c6b-b4d3-f71244cadbe9",  "slug": "string"}