Use structured logging (GSI-557)

[TheByronHimes]

Update for template changes and use the structure logging from hexkit.
This also adds a log statement in Notifier.send_notification() to catch, log, and re-raise the errors raised in _construct_email() and SmtpClient.send_email_message().

Errors are logged in the following format:

try:
  ...
except xyz as err:
  my_error = ErrorToRaise(data="123")
  log.error(my_error, extra={"data": "123"})
  raise my_error from err

It can cause some visual clutter though. Maybe we can clean up with a new approach or convenience method in the future.

[coveralls]

Pull Request Test Coverage Report for Build 7558266363

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-4.2%) to 76.19%

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Totals
Change from base Build 7102563998:	-4.2%
Covered Lines:	160
Relevant Lines:	210

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💛 - Coveralls

[mephenor]

Looks good, I just have one comment you can act upon or just leave it as is right now.