Merge Topbar location search with existing search filters

If the user is on the SearchPage, submitting a new location should
also keep the existing query params and merge the new location params
with those.

src/components/Topbar/Topbar.js

@@ -222,10 +222,12 @@ class TopbarComponent extends Component {
   }
 
   handleSubmit(values) {
+    const { currentPage, location } = this.props;
     const { search, selectedPlace } = values.location;
     const { history } = this.props;
     const { origin, bounds, country } = selectedPlace;
-    const searchParams = { address: search, origin, bounds, country };
+    const restParams = currentPage === 'SearchPage' ? parse(location.search) : {};
+    const searchParams = { ...restParams, address: search, origin, bounds, country };
     history.push(createResourceLocatorString('SearchPage', routeConfiguration(), {}, searchParams));
   }
 

src/containers/SearchPage/SearchPage.js

@@ -394,7 +394,7 @@ export class SearchPageComponent extends Component {
           mainEntity: [schemaMainEntity],
         }}
       >
-        <TopbarContainer className={topbarClasses} />
+        <TopbarContainer className={topbarClasses} currentPage="SearchPage" />
         <div className={css.container}>
           <div className={css.searchResultContainer}>
             <SearchFilters

src/containers/SearchPage/__snapshots__/SearchPage.test.js.snap

@@ -17,7 +17,9 @@ exports[`SearchPageComponent matches snapshot 1`] = `
   scrollingDisabled={false}
   title="SearchPage.schemaTitle"
 >
-  <withRouter(Connect(TopbarContainerComponent)) />
+  <withRouter(Connect(TopbarContainerComponent))
+    currentPage="SearchPage"
+  />
   <div>
     <div>
       <withRouter(InjectIntl(SearchFiltersComponent))