Adopt new status codes

[alexvanin]

It seems that node does not implement new status codes such as:

• SessionTokenNotFound
• SessionTokenExpired
• ObjectAccessDenied
• ObjectNotFound
• ObjectAlreadyRemoved
• ContainerNotFound

They all described in API and available in SDK apistatus package.

[cthulhu-rider]

Howto

"Framework" for API statuses is implemented on Signature service. This service is always the most superficial (except maybe Metrics which doesn't affect the messages), so in order to return the particular status error from the node, it can be simply returned from any level of the application code:

var errNotFound apistatus.ObjectNotFound

// fill error with some data if possible

return nil, errNotFound // server will respond with corresponding status

Nesting level

As I said error from apistatus package can be returned from any level of the server components. But while some components are meant to be used ONLY on the server side, others are not (e.g. storage engine). One might think that returning errors from apistatus package is semantically wrong, however, all package errors are declared as general purpose errors, and do not require protocol communication (the latter is just a special case of their use). So they can be freely used directly without an intermediate layer of errors.