Some modules don't expose error definitions to chain metadata

[bddap]

https://github.com/docknetwork/dock-substrate/blob/441c9128a085a5183addb9cc36eda9c2561281e6/runtime/src/attest.rs#L75 for example needs the line: type Error = Error<T>;

Without these error definitions, extrinsic submission errors are indecipherable by users. Example:

Extrinsic failed submission: [{"Module":{"index":18,"error":1}},{"weight":290004400,"class":"Normal","paysFee":"Yes"}]