include all required headers in rtr request

without an AT, there is no way to derive the tenant so it must be
pulled from the request and explicitly passed in the rtr request via the
`x-okapi-tenant` header.

src/App.js

@@ -32,7 +32,7 @@ export default class StripesCore extends Component {
     this.store = configureStore(initialState, this.logger, this.epics);
     this.actionNames = gatherActions();
 
-    registerServiceWorker(okapiConfig.url, this.logger);
+    registerServiceWorker(okapiConfig, this.logger);
   }
 
   componentWillUnmount() {

src/service-worker.js

@@ -8,6 +8,8 @@ let tokenExpiration = null;
 /** string FQDN including protocol, e.g. https://some-okapi.somewhere.org */
 let okapiUrl = null;
 
+let okapiTenant = null;
+
 /** categorical logger object */
 let logger = null;
 
@@ -109,6 +111,10 @@ const rtr = async (event) => {
 
   isRotating = true;
   return fetch(`${okapiUrl}/authn/refresh`, {
+    headers: {
+      'content-type': 'application/json',
+      'x-okapi-tenant': okapiTenant,
+    },
     method: 'POST',
     credentials: 'include',
     mode: 'cors',
@@ -332,14 +338,14 @@ self.addEventListener('activate', async (event) => {
 
 /**
  * eventListener: message
- * listen for messages from clients and dispatch them accordingly.
- * OKAPI_URL: store
+ * listen for messages from @folio/stripes-core clients and dispatch them accordingly.
  */
 self.addEventListener('message', async (event) => {
   if (event.data.source === '@folio/stripes-core') {
     console.info('-- (rtr-sw) reading', event.data);
-    if (event.data.type === 'OKAPI_URL') {
-      okapiUrl = event.data.value;
+    if (event.data.type === 'OKAPI_CONFIG') {
+      okapiUrl = event.data.value.url;
+      okapiTenant = event.data.value.tenant;
     }
 
     if (event.data.type === 'LOGGER') {

src/serviceWorkerRegistration.js

@@ -10,11 +10,11 @@
  * immediately claims control. Otherwise, no RTR would occur until after a
  * reload.
  *
- * @param {string} okapiUrl
+ * @param {object} okapi config object
  * @param {function} callback function to call when receiving any message
  * @return void
  */
-export const registerServiceWorker = async (okapiUrl, logger) => {
+export const registerServiceWorker = async (okapiConfig, logger) => {
   if ('serviceWorker' in navigator) {
     try {
       let sw = null;
@@ -42,7 +42,7 @@ export const registerServiceWorker = async (okapiUrl, logger) => {
       //
       if (sw) {
         logger.log('rtr', '<= sending OKAPI_URL', sw);
-        sw.postMessage({ source: '@folio/stripes-core', type: 'OKAPI_URL', value: okapiUrl });
+        sw.postMessage({ source: '@folio/stripes-core', type: 'OKAPI_CONFIG', value: okapiConfig });
         logger.log('rtr', '<= sending LOGGER');
         sw.postMessage({ source: '@folio/stripes-core', type: 'LOGGER', value: logger });
       } else {