Ignore "pre_alert" after "alert"

There are cases where a pre_alert record is received after an alert record, before an end record has been received. This type of de-escalation should never occur, since alert represents a higher severity level and can only be de-escalated by an end record.
This release adds logic to ignore any pre_alert records received after an alert.

This release also fixes an issue with the mobile channel where credentials may become invalid (the root cause is currently unknown). Automatic credential recreation was added when such errors are detected in order to restore the connection.

Full Changelog: v6.7.2...v6.8.2