Misc error checking issues with certificate handling in edgexproxy

[anonymouse64]

1. There is no error checking of the response code from vault. If there's an issue with accessing the certs from vault, there will be a non-200 response code and so before unmarshalling the body of the response we should be checking the response code. That would be done right after this bit of code:

security-api-gateway/core/certs.go

Lines 63 to 69 in 96482b5

	req, err := s.New().Base(secretBaseURL).Get(config.SecretService.CertPath).Request()
	resp, err := c.Do(req)
	if err != nil {
	errStr := fmt.Sprintf("Failed to retrieve certificate with path as %s with error %s", config.SecretService.CertPath, err.Error())
	return "", "", errors.New(errStr)
	}
	defer resp.Body.Close()

2. The error returned from Decode should be checked here and returned if non-nil:

security-api-gateway/core/certs.go

Line 72 in 96482b5

json.NewDecoder(resp.Body).Decode(&collection)

3. The decoded JSON should be checked to see if the certificate and the key are non-empty as they could be empty from vault, or vault could have returned some other kind of JSON object in which case the decoding would have succeeded but resulted in an empty object. That kind of check should happen just after we decode the JSON object here:

security-api-gateway/core/certs.go

Line 72 in 96482b5

json.NewDecoder(resp.Body).Decode(&collection)

4. The logger info should not be logging the cert at level Info, I think it should be a debug output, and there should be some labeling of what is being output here:

security-api-gateway/core/certs.go

Line 73 in 96482b5

lc.Info(collection.Section.Cert)

[anonymouse64]

All of these things are now checked in edgexfoundry/edgex-go#1537, so once that is merged I will close this