SQSERVICES-1126 Missing Clients (BSI Docs)

[battermann]

This covers list item 2 from this ticket

Checklist

• The PR Title explains the impact of the change.
• The PR description provides context as to why the change should occur and what the code contributes to that effect. This could also be a link to a JIRA ticket or a Github issue, if there is one.
• changelog.d contains the following bits of information (details):
  • A file with the changelog entry in one or more suitable sub-sections. The sub-sections are marked by directories inside changelog.d.

[battermann]

I tried to make the test as self-explanatory as possible, so that there is no need to write extensive comments.

[battermann]

In the ticket it says that the user should get a notification if sending of the message failed. Is there a way to test this, too. Is it necessary at all?

[fisx]

@mythsunwind FYI. (I'll also make sure the tickets will have all PRs linked by the time we consider ourselves done, then you can take a last look and second-guess me. :))

[fisx]

I merged #1989 and hereby re-approve. I think just tried locally, and I think this can be merged independently of #1869 in any order.