Add identity synchronizing code

Addresses #4475, where entries in the identities object do not
necessarily have corresponding accounts in the vault.

On password submission, this change passes known accounts to the
preferencesController (responsible for nickname management), and removes
unknown entries.

Includes "TODO" notes for where we could log the issue to sentry or
notify the user.

0 files changed, 0 insertions, 0 deletions