Add arbitrary string metadata/tags support for snapshot and other API resources #126
Description
Follow-up from PR #125 review.
Goal
Support optional user-defined string key/value metadata on API resources (starting with snapshots), similar to cloud tags.
Initial scope ideas
- Add
metadata: map[string]stringwhere appropriate in OpenAPI/resource types. - Validate key/value size and character constraints.
- Ensure metadata survives list/get/fork/restore flows.
- Add SDK exposure via Stainless.
Notes
This is intentionally out of scope for PR #125 to keep snapshot lifecycle delivery focused.