[core] Cache file source base URL and access token

This caches the base URL and access token values when they are set
so that they can still be retrieved even when the thread is paused.

test/storage/default_file_source.test.cpp

@@ -267,6 +267,22 @@ TEST(DefaultFileSource, OptionalExpired) {
     loop.run();
 }
 
+TEST(DefaultFileSource, GetBaseURLAndAccessTokenWhilePaused) {
+    util::RunLoop loop;
+    DefaultFileSource fs(":memory:", ".");
+
+    fs.pause();
+
+    auto baseURL = "http://url";
+    auto accessToken = "access_token";
+
+    fs.setAPIBaseURL(baseURL);
+    fs.setAccessToken(accessToken);
+
+    EXPECT_EQ(fs.getAPIBaseURL(), baseURL);
+    EXPECT_EQ(fs.getAccessToken(), accessToken);
+}
+
 TEST(DefaultFileSource, OptionalNotFound) {
     util::RunLoop loop;
     DefaultFileSource fs(":memory:", ".");