Feedback and CI

[julien-nc]

Nice app! You must have spent quite some time on that!
I couldn't try it against an iTop instance.

Here is the content of this PR:

• Add composer.lock to make sure all developers (and the CI actions) have the same dependency versions
• Add many CI actions
• Add Psalm config (Psalm prevents a lot of common inattention mistakes)
• Fix Psalm issues
• Add nextcloud/coding-standard composer dependency
• Fix Php coding style (run composer run cs:fix)
• Remove js build artifacts, ignore them in .gitignore
• Migrate to Vue3 + nextcloud/vue 9

Some feedback:

• The Tooltip directive was removed in nextcloud/vue 9. You can use NcPopover. I left a comment in the template of ReferenceItopWidget.vue
• You could define a Preview class that would make the preview definition stricter.
• Your PreviewMapper class could be renamed to PreviewService. We usually use *Mapper classes for database mapping.
• We can talk about the automated release process if you want
• If you have specific questions or request for recommendations, you can create an issue in your repo and send us the link in the team chat.