Update tutorial; fix lint issues

Author: cbertinato

docs/tutorials/ns1.md

@@ -97,13 +97,18 @@ spec:
         args:
         - --source=service # ingress is also possible
         - --domain-filter=example.com # (optional) limit to only example.com domains; change to match the zone created above.
+        - --ns1-zone-handle-map="example.com=corp-prod" # (optional) map example.com FQDN to corp-prod zone handle
+				- --ns1-zone-handle-map="dev.example.com=dev-view" # (optional) multiple FQDN-zone handle mappings
         - --provider=ns1
         env:
-       - name: NS1_APIKEY
+        - name: NS1_APIKEY
           valueFrom:
             secretKeyRef:
               name: NS1_APIKEY
               key: NS1_API_KEY
+        - name: EXTERNAL_DNS_NS1_ZONE_HANDLE_MAP
+          value: "example.com=corp-prod\ndev.example.com=dev-view"
+
 ```
 
 ### Manifest (for clusters with RBAC enabled)

provider/ns1/ns1.go

@@ -176,7 +176,6 @@ func (p *NS1Provider) Records(ctx context.Context) ([]*endpoint.Endpoint, error)
 			} else {
 				return nil, err
 			}
-
 		}
 
 		for _, record := range zoneData.Records {

provider/ns1/ns1_test.go

@@ -424,9 +424,9 @@ func TestNS1ChangesByZone_IgnoresUnmatchedRecords(t *testing.T) {
 
 	// Should still have exactly the zone keys for the provided zones, but no entries inside.
 	if gs, ok := changes["foo-handle"]; ok {
-		assert.Len(t, gs, 0)
+		assert.Empty(t, gs)
 	}
 	if gs, ok := changes["bar.com"]; ok {
-		assert.Len(t, gs, 0)
+		assert.Empty(t, gs)
 	}
 }