Allow to join an open group

Also:

* Refactor interacting with a remote event so that you can interact with
  a remote group as well
* Add a setting for group admins to pick between an open and invite-only
  group
* Fix new groups without posts/todos/resources/events/conversations URL
  set
* Repair local groups that haven't got their
  posts/todos/resources/events/conversations URL set
* Add a scheduled job to refresh remote groups every hour
* Add a user setting to pick when to receive notifications when there's
  new members to approve (will be used when this feature is available)
* Fix pagination for members

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

js/src/views/Event/Participants.vue

@@ -185,12 +185,8 @@
 
 <script lang="ts">
 import { Component, Prop, Vue, Watch, Ref } from "vue-property-decorator";
-import {
-  IEvent,
-  IEventParticipantStats,
-  IParticipant,
-  ParticipantRole,
-} from "../../types/event.model";
+import { IParticipant, ParticipantRole } from "../../types/participant.model";
+import { IEvent, IEventParticipantStats } from "../../types/event.model";
 import { PARTICIPANTS, UPDATE_PARTICIPANT } from "../../graphql/event";
 import { CURRENT_ACTOR_CLIENT } from "../../graphql/actor";
 import { IPerson, usernameWithDomain } from "../../types/actor";