Force SSL on App Engine Flexible Environment Custom Runtime : <p>We're running an instance of Metabase on a App Engine Flexible Custom Runtime with a Dockerfile based on openjdk:8. Currently it allows access on <a href="http://[metabase-project].appspot.com/" rel="noreferrer">http://[metabase-project].appspot.com/</a> and <a href="https://[metabase-project].appspot.com/" rel="noreferrer">https://[metabase-project].appspot.com/</a>. I'd like to force SSL by having all http traffic redirected to https.</p>

<p>The Dockerfile looks something like this:</p>

<pre><code>FROM openjdk:8
ADD https://dl.google.com/cloudsql/cloud_sql_proxy.linux.amd64 ./cloud_sql_proxy
ADD http://downloads.metabase.com/v0.21.1/metabase.jar ./metabase.jar
CMD ./cloud_sql_proxy -instances=$INSTANCE=tcp:$MB_DB_PORT -dir=/cloudsql &amp; java -jar ./metabase.jar
</code></pre>

<p>Our app.yaml looks like:</p>

<pre><code>service: metabase
runtime: custom
env: flex
</code></pre>

<p>In a normal App Engine app.yaml file, I'd want to add:</p>

<pre><code>handlers:
- url: [something]
  secure: always
</code></pre>

<p>But in the custom runtime we don't have access to handlers like this. Is there a way to configure the Flexible runtime to perform the redirect for all traffic?</p>
