Rudder

Due to the way items are deserialized.

The other problem is that higher level diagnostics can't refer to a source line.

No simple fix:

• https://github.com/dtolnay/serde-yaml/issues/128
• https://github.com/faradayio/openapi-interfaces/issues/28

Leads:

• Patch in https://github.com/chyh1990/yaml-rust/issues/103
• And for source markers https://github.com/chyh1990/yaml-rust/pull/125

We can start with a simple solution, which it to deserialize into a simpler structure to handle basic stuff, and then convert to the actual technique and manually handle errors.