That url isn’t correct. You are trying to use an OH 1.x url. OH 2 supports many UIs now so the urls have changed.
First of all, if you go to localhost:8090 you should see a list of UIs that have been installed. Among these you should see BasicUI and/or ClassicUI. If not you need to install the UI of you choice (you can do this through PaperUI or adding it to addons.cfg).
Now when you go to localhost:8090 you will see these UIs listed. When you click on, lets say BasicUI, you will see the url becomes:
http://localhost:8090/basicui/app
If you haven’t set a default sitemap you may need to supply one:
http://localhost:8090/basicui/app?sitemap=mysitemap
Classic UI works the same only replace basicui with classicui.
See the following for some more lessons learned on running OH in Docker.