- As the tracker img in the body is currently also used to set the
X-Odoo-MailTracking-ID mail header we can remove the tag only
after this is done
- Added tests to check for the presence and absence of the tracking
image tag depending on the new configuration parameter
- Any model inheriting from mail.thread will have a filter available to
obtain records with errors in their messages trackings.
- The messages can be marked as done to avoid false positives when the
issues are solved.