[BPO] libreoffice 7.3.7 for bionic

[Rico Tzschichholz]

[Impact]

 * LibreOffice 7.3.7 is in its seventh bugfix release of the 7.3 line:
     https://wiki.documentfoundation.org/ReleasePlan/7.3#7.3.7_release

 * This source packages matches the proposed SRU for jammy handled at
     https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/1995054
   and its backport is currently provided by the LibreOffice Still PPA at
     https://launchpad.net/~libreoffice/+archive/ubuntu/libreoffice-still/+packages

 * Previous backport of 7.3.6 handled at
     https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/1990382

 * LibreOffice 6.4.7 (EOL since November 30, 2020) is currently released in focal.
 * LibreOffice 7.3.6 is currently released in bionic-backports.

 * Given the nature of the project, the complexity of the codebase and the high level of quality assurance upstream, it is preferable to SRU a minor release rather than cherry-pick selected bug fixes.

[Scope]

 * Backport of https://launchpad.net/ubuntu/+source/libreoffice/1:7.3.7-0ubuntu0.22.04.1

 * Backport target is Bionic/18.04 LTS only to provide an official build of a more recent upstream version of LibreOffice

[Testing]

 * Upstream testing. Bugs fixed upstream typically include unit/regression tests, and the release itself is extensively exercised (both in an automated manner and manually).

  * A recent set of upstream's automated jenkins testing can be found here:
    https://ci.libreoffice.org/job/gerrit_73/2020/

  * More information about the upstream QA testing can be found here:
    * Automated tests
      https://wiki.documentfoundation.org/QA/Testing/Automated_Tests
    * Automated UI tests
      https://wiki.documentfoundation.org/Development/UITests
    * Regression tests
      https://wiki.documentfoundation.org/QA/Testing/Regression_Tests
    * Feature tests
      https://wiki.documentfoundation.org/QA/Testing/Feature_Tests

 * Launchpad testing. The libreoffice packages include autopkgtests that were run and verified as passing.
    * [amd64] https://autopkgtest.ubuntu.com/results/autopkgtest-bionic-libreoffice-experimental/bionic/amd64/libr/libreoffice/20221109_194619_aafcb@/log.gz
    * [arm64] https://autopkgtest.ubuntu.com/results/autopkgtest-bionic-libreoffice-experimental/bionic/arm64/libr/libreoffice/20221109_182935_ad523@/log.gz
    * [armhf] https://autopkgtest.ubuntu.com/results/autopkgtest-bionic-libreoffice-experimental/bionic/armhf/libr/libreoffice/20221109_193157_bfaf9@/log.gz
    * [i386] https://autopkgtest.ubuntu.com/results/autopkgtest-bionic-libreoffice-experimental/bionic/i386/libr/libreoffice/20221110_005928_4e278@/log.gz
    * [ppc64el] https://autopkgtest.ubuntu.com/results/autopkgtest-bionic-libreoffice-experimental/bionic/ppc64el/libr/libreoffice/20221109_191816_d9338@/log.gz
    * [s390x] https://autopkgtest.ubuntu.com/results/autopkgtest-bionic-libreoffice-experimental/bionic/s390x/libr/libreoffice/20221109_173606_13453@/log.gz

 * General smoke testing of all the applications in the office suite were carried out by going through the manual testplan as documented by: https://wiki.ubuntu.com/Process/Merges/TestPlans/libreoffice

[Regression Potential]

 * A minor release with a total of 28 bug fixes always carries the potential for introducing regressions, even though it is a bugfix-only release, meaning that no new features were added, and no existing features were removed.

 * A combination of autopkgtests and careful smoke testing as described above should provide reasonable confidence that no regressions sneaked in.