The motivation is to reduce code complexity, get rid of the extra IMAP connection and cases when
messages are added to chats by Inbox and Sentbox loops in parallel which leads to various message
sorting bugs, particularly to outgoing messages breaking sorting of incoming ones which are fetched
later, but may have a smaller "Date".
This change removes OAuth2 for Gmail
as Delta Chat does not have a working
client ID anymore.
Tests are adjusted to test against Yandex
and MX queries for OAuth2 are always disabled
because they were only used to detect Google Workspace.
scripts/update-provider-database.sh checks out the provider database
and updates data.rs file,
making it easier to update.
CI uses this script to check that checked in data.rs
corresponds to the provider database repository.
