[api] work on mail content for BuildFail emails
[webui] test for notification defaults
[api] 2 small fixes for the test suite
[api] test build failure mail
[api] put the log file in raw mode in the mail

HTML escaping is cool - outside of mails :)
[api] include some headers in the build fail mail header
[api] add threading support for build failure mails

And enable actual sendmail
[api] allow "noservice" parameter for source copy calls and test it
[api] some changes to the event mails

- don't set reply-to but from
- put all receivers in the same email, so they can share thoughty by group-reply
- use realnames in mail headers
[api] fix comment emails
[api] change the subject of the request event mails
[api] message-ids contain < and >
[api] avoid sending bounces to obs users
[api] fix another mail fixture
[api] also add a Sender to the mail headers
[doc] add oproject parameter to project copy
[api] allow to accept set_bugowner requests also in locked projects and packages, _if_ using force=1.

This is required to change responsible after a release has been created
[api] use a consistent domain in message ids
[backend] add the information to the build event if a failed log file exists
[webui] don't offer reply link to nobody