refactor: Don't request a new access token unless needed

app/src/main/java/com/p_vacho/neat_calendar/MainActivity.kt

@@ -57,9 +57,12 @@ class MainActivity : AppCompatActivity() {
 
     private suspend fun checkUserLogin(): Boolean {
         if (authRepository.validateRefreshToken() != null) {
-            // Get a brand new access token (even if the old access token is still valid,
-            // it's better to just get a new one so it doesn't expire as quickly on us)
-            return authRepository.refreshAccessToken()
+            if (authRepository.validateAccessToken() == null) {
+                // In case access token is already invalid, request a new one
+                return authRepository.refreshAccessToken()
+            }
+            // Access token still valid, we're already logged in
+            return true
         }
         return false
     }