feat: invites regardless of registration type, invite privilege, groups to join on acceptance (#8786)

* feat: allow invites in normal registration mode + invite privilege

* feat: select groups to join from an invite

* test: check if groups from invitations have been joined

* fix: remove unused variable

* feat: write API versions of socket calls

* docs: openapi specs for the new routes

* test: iron out mongo redis difference

* refactor: move inviteGroups endpoint into write API

* refactor: use GET /api/v3/users/:uid/invites/groups

Instead of GET /api/v3/users/:uid/inviteGroups

* fix: no need for /api/v3 prefix when using api module

* fix: tests

* refactor: change POST /api/v3/users/invite

To POST /api/v3/users/:uid/invites

* refactor: make helpers.invite awaitable

* fix: restrict invite API to self-use only

* fix: move invite groups controller to write api, +tests

* fix: tests

Co-authored-by: Julian Lam <julian@nodebb.org>

src/views/admin/manage/users.tpl

@@ -3,9 +3,9 @@
 		<div class="clearfix">
 
 			<div class="pull-left">
-				<!-- IF inviteOnly -->
+				<!-- IF showInviteButton -->
 				<button component="user/invite" class="btn btn-success"><i class="fa fa-users"></i> [[admin/manage/users:invite]]</button>
-				<!-- ENDIF inviteOnly -->
+				<!-- ENDIF showInviteButton -->
 				<a target="_blank" href="{config.relative_path}/api/admin/users/csv" class="btn btn-primary">[[admin/manage/users:download-csv]]</a>
 				<div class="btn-group">
 					<button class="btn btn-default dropdown-toggle" data-toggle="dropdown" type="button">[[admin/manage/users:edit]] <span class="caret"></span></button>