Start on project with the connection services and first command to list databases

config/services.yaml

@@ -23,3 +23,9 @@ services:
 
     # add more service definitions when explicit configuration is needed
     # please note that last definitions always *replace* previous ones
+
+    App\Service\MysqliConnection:
+        arguments:
+            $hostname: '%env(string:DATABASE_HOSTNAME)%'
+            $user: '%env(string:DATABASE_USER)%'
+            $password: '%env(DATABASE_PASSWORD)%'