Ch.I.CredentialsStorage is disabled, since it's not an official interface
and would be difficult to compile. From what I know, it's only useful if we
wish to be able to store credentials provided to telepathy and unrelated to
any libaccounts account in libsignon, which isn't relevant for the use case
here.

TLS channels are disabled and certificate validation is left to CMs.

OAUTH2 mechanisms are disabled right now to force the use of password
authentication; that's expected to change.