refactor: display TLS

* refactor(backend): fix duplicated process req
* feat: clean db leftovers
* detect properly duplicated port
* refactor: store id_vm + port
* refactor(test): check port conflict
* refactor(test): copy config for mock domains
* check enforce limits properly
* check better port conflicts
* fix(install): correct id_vm
* properly test TLS
* : store port and vm to check duplicates
* show displays TLS
* clean cache when desconnecting VMs
* test: allow link sizes attribute
* test(displays): check gone TLS display when migrating
* install: clean ports before create index
* test ports with rvd_back running
* make sure there is an n_order field
*test ports and unload nbd when testing spinoff
* install: clean duplicated indexes
* refactor(test): tet mojo in background
* refactor(frontend): hide display URL unless port
* vlc no TLS
* refactor(test): clean iptables after test
* refactor(ports): improved fix conflict
* refactor(ports): manage secondary displays
* refactor: remove display_file pre-generated
* cache connections only if writeable
* user may have been removed
* retry 10 times to solve conflict