Heroku Postgresql with Google Datastudio

I'm having troubles to connect an existing heroku database to Google Datastudio. I'm trying to add the connection and I get the following:

Access denied, please check your username and password.

Now, I'm 100% sure that I'm correct on those credentials and the problem comes from somewhere else.

I've tried with different setup, either a free or a paid PSQL instance, nothing works.

I've also setup a dummy account on elephantsql and the connection worked the first time without any issue.

Do you have any idea of the cause of that problem?

Edit:

Just found https://www.en.advertisercommunity.com/t5/Data-Studio/Heroku-Postgres-lt-gt-Google-Data-Studio/m-p/1031729 which is not helpful at the time of writing this post.

Since the February 6, 2018 update, Google DataStudio allows SSL connections with PostgreSQL, which is necessary to connect to a database created via Heroku.

To enable SSL you need to provide client key+cert and server cert, which can be accomplished by taking the following steps:

1. Generate a self-signed cert + key with openssl for client key + certificate:

openssl req \
       -newkey rsa:2048 -nodes -keyout client.key \
       -x509 -days 365 -out client.crt

2. Use the postgres_get_server_cert.py script to get the self-signed server cert from heroku psql:

https://raw.githubusercontent.com/thusoy/postgres-mitm/master/postgres_get_server_cert.py