dbbackup authentication failed !?

[zaggash]

Hi.

I read 2/3 things about DB_AUTH but I'm not sure I understand the purpose of it.

When I create a backup of my container the logs reports:

2024-04-25 22:05:47.270 UTC [17381] FATAL:  password authentication failed for user "dbbackup"
2024-04-25 22:05:47.270 UTC [17381] DETAIL:  Role "dbbackup" does not exist.
	Connection matched pg_hba.conf line 100: "host all all all scram-sha-256"

However I never specified a dbbackup user anywhere either on db_backup container nor postgres container.
My postgres container is started and created with postgres as user and somerandomname as db_name like:

POSTGRES_DB: somerandomname
POSTGRES_USER: postgres

However I'm using DB01_NAME: ALL and DB01_SPLIT_DB: false in the db_backup container.

Anyone to help me understand ?
Thanks