Resolve "add support for debian:buster"

Closes #879 (closed), #77 (closed), #828 (closed)

changed milestone to %v14.0.0~alpha.1

added enhancement label

changed the description

added 4 commits

• 9b0ec4c8 - support for tomcat9 added
• 3d3e5267 - force upgrade of tomcat to at least tomcat8
• 3bb5ac20 - we can test on latest debian again
• da77bde0 - reference to tomcat7 removed

Compare with previous version

unmarked as a Work In Progress

enabled an automatic merge when the pipeline for da77bde0 succeeds

mentioned in commit e36db602

merged