Add additional unwrap code in ToStatusError() gRPC error handler

[krapie]

What this PR does / why we need it:

Add additional unwrap code in TostatusError() in grpchelper/status.go which unwrap’s error until cause is set to base inner error.

This additional code is needed to avoid errorToCode map’s hash of unhashable type runtime error which leads to server panic.

This will prevent Yorkie server(Yorkie SaaS API) to panic(service unavailable) on unexpected error triggered by user.

Below is ToStatusError()’s parameter, err’s inner stacks(errors)

error(*fmt.wrapError) *{
    	msg: "decode project info: connection(localhost:27017[-12]) incomplete read of message header: context canceled",
	err: error(go.mongodb.org/mongo-driver/mongo.CommandError) {
		Code: 0,
		Message: "connection(localhost:27017[-12]) incomplete read of message header: context canceled",
		Labels: []string len: 1, cap: 1, ["NetworkError"],
		Name: "",
		Wrapped: error(go.mongodb.org/mongo-driver/x/mongo/driver/topology.ConnectionError) *{
			ConnectionID: "localhost:27017[-12]",
			Wrapped: error(*errors.errorString) *{
				s: "context canceled"
			},
			init: false,
			message: "incomplete read of message header"
		},
		Raw: go.mongodb.org/mongo-driver/bson.Raw len: 0, cap: 0, nil
	}
}

Parameter err needs to be unwrapped to base inner error. If not, errorToCode[cause] map (maps error to gRPC status code) will get invalid key for map like errorToCode[mongo.CommandError] which will lead to server panic: runtime error: hash of unhashable type mongo.CommandError.

This runtime error will occur when parameter err has nested errors (ex: mongo.CommandError)

Which issue(s) this PR fixes:

No issue is related.

Special notes for your reviewer:

This PR started with server log provided by @hackerwins on discord thread on unexpected server down issue.

Also, I'm not sure about the initial cause of this error, which makes connection(localhost:27017[-12]) incomplete read of message header: context canceled error. I'll keep trying to reproduce this issue in code ASAP.

Does this PR introduce a user-facing change?:

NONE

Additional documentation:

Checklist:

• Added relevant tests or not required
• Didn't break anything

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #434 (b12c8a9) into main (a558c0f) will not change coverage.
The diff coverage is n/a.

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##             main     #434   +/-   ##
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  Coverage   46.96%   46.96%           
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  Files          71       71           
  Lines        5913     5913           
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  Hits         2777     2777           
  Misses       2831     2831           
  Partials      305      305           

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[hackerwins]

Thanks for your contribution. 👍 I looked at the relevant code a bit more.

ToStatusError receive internal errors defined in Yorkie. They seem to be two patterns.

Case 1: Convert MongoDB error into an internal error

	if err := result.Decode(&info); err != nil {
		if err == mongo.ErrNoDocuments {
			return nil, fmt.Errorf("default: %w", database.ErrProjectNotFound)
		}
	}

Case 2: Use MongoDB error as cause

	client, err := mongo.Connect(ctx)
	if err != nil {
		return nil, fmt.Errorf("connect to mongo: %w", err)
	}

The previous code seems to work only for Case 1. I think we can avoid both cases if we return the root cause like this PR.

[hackerwins]

LGTM