The etherpad component's nginx configuration needs to know the request
scheme in order to set some variables that influence whether the
'Secure' flag is set on cookies. Right now it directly uses the $scheme
variable, but this variable does not get set to the expected value if
nginx is behind a reverse-proxy where the proxy handles TLS termination.
Adjust the etherpad nginx config to use a variable with a different name
$real_scheme, which can be set in the nginx server block to match the
configuration of the nginx listeners.
This variable is set to the value of $scheme in the default
/etc/sites-available/bigbluebutton file. The bbb-install.sh script will
be updated to set this variable in the configurations it writes.
People using other installation scripts will need to add this variable
to their nginx configuration file, or etherpad might not operate correctly.
