Currently, almost our v1 Operator API return value type
is v1::master::Response.
Now we validation `Call` by `validation::master::call::validate(call,
principal)` and return `BadRequest` if it could not pass.
In some cases, we need to validate the `Call` with other parameters. For
example,
```
Option<Error> validate = validation::operation::validate(
operation.create(), slave->checkpointedResources, principal);
```
1. Could we delegate this validation into the implementation of API? If
delegate the validation to API, the return type would be
`process::http::Response` because of `BadRequest` could not convert to
`v1::master::Response`.
2. And for keep consistent, should we change existing RPC handlers' return
type to `v1::master::Response` as well?
--
Best Regards,
Haosdent Huang
