Author a Storage Plugin

Goal

Implement a backend plugin that advertises truthful capabilities, streams bytes without buffering whole objects, maps errors into ovstorage codes, and passes the plugin conformance harness.

Recipe

1. Start with docs/public/plugin-development/README.md for the shared C ABI, manifest, loader, and build loop.
2. Use docs/public/plugin-storage/README.md for the storage-specific Factory and Backend contract.
3. Mirror a small reference plugin such as ovstorage-plugin-http before introducing vendor SDK complexity. (The file backend is built into the library, not a plugin crate, so it is not a template for a loadable plugin.)
4. Set capability bits only for operations the backend actually honors.
5. Add streaming-invariant coverage for any streaming read or write path.
6. Run make verify before merge.

Review Checks

• Manifest name/version come from Cargo package metadata.
• Secrets only travel through credential fields or credential providers.
• Write success means durable backend state is visible to a following read.
• Unsupported operations return Unsupported and do not advertise the matching capability.