I have TLS enabled on my postgresql DB and both registry and match talk to it (or I was hoping for that).  registry does talk to it but NOT using a TLS connection (even with sslmode set to allow in database.php.  Match fails to talk to the DB until I specify sslmode allow in database.php but there is no way via the container environment to pass in this setting.  Both match and registry database.php are similar (here is what I used for match generated by the docker ENV vars and then I modified the file while the container was running):

    'Datasources' => [

      'default' => [

      'className' => 'Cake\Database\Connection',

      'driver' => 'Cake\Database\Driver\Postgres',

      'host' => 'pgm',

      'username' => 'match',

      'password' => 'xxxxxxx',

      'database' => 'match',

      'sslmode' => 'allow',

      ]