Migrate from Vue 2 to Vue 3

[ChristophWurst]

Describe the task

https://v3-migration.vuejs.org/

Exemplary migration: nextcloud/spreed#9448

Affected components

Calendar, Calendar Resource Management, Contacts, Mail, Calendar-availability-vue

Preparation

• Fix Vue 2.7 deprecations
  • Migrate deep selector (::v-deep to :deep) calendar#5693
  • Migrate deep selector (::v-deep to :deep) contacts#3786
  • Migrate deep selector (::v-deep to :deep) mail#9242
  • Migrate deep selector (::v-deep to :deep) calendar-availability-vue#212
  • Migrate deprecated slot syntax calendar#5694
  • Migrate deprecated slot syntax mail#9243
  • Migrate deprecated slot syntax contacts#3787
  • Replace Vuex with pinia
    • Replace global Vuex store with Pinia mail#9237
    • Replace outbox Vuex store with Pinia mail#9238
    • Replace appointments config Vuex store with Pinia calendar#5685
    • Replace global Vuex store with Pinia calendar#5686
    • Replace Vuex store with Pinia contacts#3781
  • Replace global event buses with mitt #75
• Replace components libs that have no vue 3 support

Upgrades

• Vue 3 for nextcloud/calendar-availability-vue
• Vue 3 in apps

To do

to be defined

[ChristophWurst]

Related: nextcloud-libraries/nextcloud-vue#3692

[ChristophWurst]

We can take inspiration from nextcloud/spreed#9448 for a less bumpy upgrade path and changes we can do while staying on Vue 2.7.

[ChristophWurst]

nextcloud/calendar-availability-vue does not need adjustments for Vue 3 accoring to @GVodyanov. Removing it from the list of affected components.