Add Security Warning Bar for untrusted notebooks (#970)

* Add Security Warning Bar for untrusted notebooks

* Update

* Another update

* Add a snapshot test

* UX updates

* More updates

* Add tests

* Update test snapshot

* Update string

* Update security message

src/Explorer/Notebook/SecurityWarningBar/SecurityWarningBar.test.tsx

@@ -0,0 +1,31 @@
+import { shallow } from "enzyme";
+import React from "react";
+import { SecurityWarningBar } from "./SecurityWarningBar";
+
+describe("SecurityWarningBar", () => {
+  it("renders if notebook is untrusted", () => {
+    const wrapper = shallow(
+      <SecurityWarningBar
+        contentRef={"contentRef"}
+        isNotebookUntrusted={true}
+        markNotebookAsTrusted={undefined}
+        saveNotebook={undefined}
+      />
+    );
+
+    expect(wrapper).toMatchSnapshot();
+  });
+
+  it("renders if notebook is trusted", () => {
+    const wrapper = shallow(
+      <SecurityWarningBar
+        contentRef={"contentRef"}
+        isNotebookUntrusted={false}
+        markNotebookAsTrusted={undefined}
+        saveNotebook={undefined}
+      />
+    );
+
+    expect(wrapper).toMatchSnapshot();
+  });
+});