PuppetDB does not support username@hostname auth for Azure PostgreSQL

As a customer, I want to be able to use Azure PostgreSQL as my external PostgreSQL database for Puppet Enterprise.
 
When attempting to use Azure PostgreSQL as an external database for PuppetDB (PE 2019.8.1), I encountered the problem that Azure requires the username for the Postgres connection to be in the username@hostname form, due to the way they publish access to PostgreSQL (as described here). I can manually modify database.ini to set the username to that format, but then you’ll see this in the logs:

clojure.lang.ExceptionInfo: Connected to database as "pe-puppetdb-migrator", not migrator "pe-puppetdb-migrator@pdb01"

It seems we have the same limitations as Chef has (see linked issue).
 
This requirement from Azure stems from their architecture:

Azure Database for PostgreSQL has a gateway in front of the actual database servers that forwards connections from username@hostname to hostname as username.

This means that once the connection is established, you will actually be connected as username, not username@hostname, and any database queries involving users should just use username (e.g. granting permissions).

 
Some issues I’ve encountered while trying to get this to work:

• The docs don’t tell you to also create a pe-puppetdb-migrator user
• The docs assume a Linux OS for the psql commands to create the users & databases. However, Azure PostgreSQL runs on Windows, which causes the locales to have different names. For Azure PostgreSQL, the ENCODING line needs to be changed to: ENCODING 'utf8' LC_CTYPE 'English_United States.1252' LC_COLLATE 'English_United States.1252' template template0;
• You can’t specify username@hostname for the xxx_regular_db_user and xxx_migration_db_user settings in pe.conf, the @hostname part gets cutoff during installation.
• I can manually re-add the @hostname back to the username in database.ini but then the queries also expect this for the connection, which they should not. And I can probably assume that another puppet run would overwrite the settings in database.ini again.