[ticket/12975] Fix the construction of phpbb\auth\provider\db for Oauth

PHPBB3-12975
Merge pull request #2872 from Nicofuma/ticket/12975

[ticket/12975] Fix the construction of phpbb\auth\provider\db for Oauth

* Nicofuma/ticket/12975:
  [ticket/12975] Fix the construction of phpbb\auth\provider\db for Oauth
[ticket/12988] Make all the services private and replace them with alias

PHPBB3-12988
[ticket/12988] Handle aliases in service_collection

PHPBB3-12988