Place Jupyterhub configuration in a fixed known location

Previously we relied on the config file being in the same working directory
as the Jupyterhub command was invoked from, which is brittle. This
places the config in a known location and explicitly passes the path
when starting Jupyterhub.

docker/Dockerfile

@@ -67,7 +67,7 @@ RUN pip install /tmp/dataprocspawner/
 COPY static/templates/ /etc/jupyterhub/templates/
 COPY static/mdc/ /usr/local/share/jupyterhub/static/mdc/
 
-COPY docker/jupyterhub_config.py .
+COPY docker/jupyterhub_config.py /etc/jupyterhub/jupyterhub_config.py
 
 EXPOSE 8080
 

docker/jupyterhub.sh

@@ -271,4 +271,4 @@ function set-default-name-pattern() {
 append-to-jupyterhub-config
 
 # Starts JupyterHub.
-jupyterhub
+jupyterhub -f /etc/jupyterhub/jupyterhub_config.py