Migrate to vue3

We should migrate to vue3, but there are still plugins not available for vue3

• The keycloak plugin is beta https://github.com/dsb-norge/vue-keycloak-js
• If there will be a cytoscape implementation for vue3 is not yet clear https://github.com/rcarcasses/vue-cytoscape/issues/96
• Bootstrap-vue3 still in development and alpha https://cdmoro.github.io/bootstrap-vue-3/reference/parityList.html#slots-34

We can't migrate now. I doubt if we ever migrate. The ecosystem of vue2 moves very slow and the stuff behind vue is just way too fast.