refactor(feg) replace deprecated errors module

Replace further calls to github.com/pkg/errors module with fmt
equivalents. Created in pairing with Moritz Huebner.

Signed-off-by: Sebastian Wolf <sebastian.wolf@tngtech.com>

feg/cloud/go/services/feg/obsidian/models/validate.go

@@ -32,7 +32,7 @@ func (m FegNetworkID) ValidateModel(ctx context.Context) error {
 	if !swag.IsZero(m) {
 		exists, err := configurator.DoesNetworkExist(ctx, string(m))
 		if err != nil {
-			return fmt.Errorf(fmt.Sprintf("Failed to search for network %s: %w", string(m)), err)
+			return fmt.Errorf(fmt.Sprintf("Failed to search for network %s", string(m))+": %w", err)
 		}
 		if !exists {
 			return errors.New(fmt.Sprintf("Network: %s does not exist", string(m)))
@@ -49,7 +49,7 @@ func (m *FederatedNetworkConfigs) ValidateModel(ctx context.Context) error {
 	if !swag.IsZero(nid) {
 		exists, err := configurator.DoesNetworkExist(ctx, nid)
 		if err != nil {
-			return fmt.Errorf(fmt.Sprintf("Failed to search for network %s: %w", nid), err)
+			return fmt.Errorf(fmt.Sprintf("Failed to search for network %s", nid)+": %w", err)
 		}
 		if !exists {
 			return fmt.Errorf("Network: %s does not exist", nid)

feg/radius/lib/go/oc/server_options.go

@@ -22,7 +22,6 @@ import (
 	"contrib.go.opencensus.io/exporter/prometheus"
 	"fbc/lib/go/http/server"
 	"fbc/lib/go/oc/helpers"
-	"github.com/pkg/errors"
 	prom_client "github.com/prometheus/client_golang/prometheus"
 	"go.opencensus.io/plugin/ochttp"
 	"go.opencensus.io/stats/view"