Migrate get-api-url module to TS

src/sidebar/config/get-api-url.js → src/sidebar/config/get-api-url.ts

-/** @typedef {import('../../types/config').SidebarSettings} SidebarSettings */
+import type { SidebarSettings } from '../../types/config';
 import { serviceConfig } from './service-config';
 
 /**
  * Function that returns apiUrl from the settings object.
  *
- * @param {SidebarSettings} settings - The settings object
- * @return {string} The apiUrl from the service or the default apiUrl from the settings
+ * @return The apiUrl from the service or the default apiUrl from the settings
  * @throws {Error} If the settings has a service but the service doesn't have an apiUrl
- *
  */
-export function getApiUrl(settings) {
+export function getApiUrl(settings: SidebarSettings): string {
   const service = serviceConfig(settings);
+  if (!service) {
+    return settings.apiUrl;
+  }
 
-  if (service) {
-    // If the host page contains a service setting then the client should default to
-    // using that apiUrl.
+  // If the host page contains a service setting then the client should default
+  // to using that apiUrl.
   if (service.apiUrl) {
     return service.apiUrl;
-    } else {
-      throw new Error('Service should contain an apiUrl value.');
   }
-  }
-  return settings.apiUrl;
+
+  throw new Error('Service should contain an apiUrl value.');
 }