FEATURE: Allow scoping search to tag (#8345)

* When viewing a tag, the search widget will now show a checkbox to scope the search by tag, which will limit search results to that tag on desktop and mobile

test/javascripts/lib/search-test.js.es6

@@ -1,4 +1,7 @@
-import { translateResults } from "discourse/lib/search";
+import {
+  translateResults,
+  searchContextDescription
+} from "discourse/lib/search";
 
 QUnit.module("lib:search");
 
@@ -31,3 +34,27 @@ QUnit.test("unescapesEmojisInBlurbs", assert => {
   assert.ok(blurb.indexOf("<img src") === 0);
   assert.ok(blurb.indexOf(":thinking:") === -1);
 });
+
+QUnit.test("searchContextDescription", assert => {
+  assert.equal(
+    searchContextDescription("topic"),
+    I18n.t("search.context.topic")
+  );
+  assert.equal(
+    searchContextDescription("user", "silvio.dante"),
+    I18n.t("search.context.user", { username: "silvio.dante" })
+  );
+  assert.equal(
+    searchContextDescription("category", "staff"),
+    I18n.t("search.context.category", { category: "staff" })
+  );
+  assert.equal(
+    searchContextDescription("tag", "important"),
+    I18n.t("search.context.tag", { tag: "important" })
+  );
+  assert.equal(
+    searchContextDescription("private_messages"),
+    I18n.t("search.context.private_messages")
+  );
+  assert.equal(searchContextDescription("bad_type"), null);
+});