FirebaseStub refactoring

__mocks__/gatsby-plugin-firebase/constants/auth.js

@@ -0,0 +1,19 @@
+class Auth {
+  static anonymousUser1 = {
+    displayName: 'Anonymous User 1',
+    email: 'anonymous1@noemail.com',
+    isAnonymous: true,
+    name: 'Anonymous 1',
+    uid: 'anonym123',
+  };
+
+  static anonymousUser2 = {
+    displayName: 'Anonymous User 2',
+    email: 'anonymous2@noemail.com',
+    isAnonymous: true,
+    name: 'Anonymous 2',
+    uid: 'anonym456',
+  };
+}
+
+export { Auth };