Description of problem:

The spawner UI can be launched by one user for another user (via the admin page). When this occurs the config map with the launcher options that is created is for the logged in user not the user the spawner is being launched for so the notebook server created is not created with the correct settings.

Steps to Reproduce

1. Launch the spawner UI as an admin
2. Go to the Admin page
3. Click 'start server' for a different user
4. In the spawner UI update the settings
5. Start the server

Actual results:

The config map `jupyterhub-singleuser-profile-<logged in username>` is updated to the selected settings.

The config map `jupyterhub-singleuser-profile-<for username>` is not updated or not present.

The progress page shows invalid selections (or an error)

Expected results:

The config map `jupyterhub-singleuser-profile-<for username>` is updated to the selected settings.

The progress page shows correct info and launches the server.

Reproducibility (Always/Intermittent/Only Once):

always