Allow passing in notification channel name & description as strings on DownloadService

Use case description

We'd like to make use of the DownloadService and take advantage of the ability to have the Service itself create the Notification Channel for us, but can't rely on string resources for notification channel name & description.

Proposed solution

Add an additional constructor to DownloadService that rather than taking in a String resource for channel name and description, would take String or CharSequence instead. This way implementors can use their own localization mechanism, not having to give up on this feature and rely on creating the notification channel themselves.

Proposed constructor

 protected DownloadService(
      int foregroundNotificationId,
      long foregroundNotificationUpdateInterval,
      @Nullable String channelId,
      String channelName,
      String chanelDescription)

Alternatives considered

Currently the only option to circumvent this inconvenience is to use the simpler cosntructor:

protected DownloadService(
      int foregroundNotificationId, long foregroundNotificationUpdateInterval)

and to create the notfiication channel separately.