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>

public/openapi/write/users/uid/invites.yaml

@@ -0,0 +1,48 @@
+post:
+  tags:
+    - users
+  summary: invite users with email by email
+  description: This operation sends an invitation email to the given addresses, with an option to join selected groups on acceptance
+  parameters:
+  - in: path
+    name: uid
+    schema:
+      type: integer
+    required: true
+    description: uid of the user sending invitations
+    example: 1
+  requestBody:
+    required: true
+    content:
+      application/json:
+        schema:
+          type: object
+          properties:
+            emails:
+              type: string
+              description: A single or list of comma separated email addresses
+              example: friend01@example.com,friend02@example.com
+            groupsToJoin:
+              type: array
+              description: A collection of group names
+              example: ['administrators']
+          required:
+            - emails
+  responses:
+    '200':
+      description: invitation email(s) sent
+      content:
+        application/json:
+          schema:
+            type: object
+            properties:
+              status:
+                $ref: ../../../components/schemas/Status.yaml#/Status
+              response:
+                type: object
+    '400':
+      $ref: ../../../components/responses/400.yaml#/400
+    '401':
+      $ref: ../../../components/responses/401.yaml#/401
+    '403':
+      $ref: ../../../components/responses/403.yaml#/403

public/openapi/write/users/uid/invites/groups.yaml

@@ -0,0 +1,23 @@
+get:
+  tags:
+    - users
+  summary: Get group names that the user can invite
+  parameters:
+    - in: path
+      name: uid
+      schema:
+        type: integer
+      required: true
+      description: uid of the user to make the query for
+      example: 1
+  responses:
+    '200':
+      description: A collection of group names returned
+      content:
+        application/json:
+          schema:
+            type: array
+            items:
+              type: string
+    '401':
+      $ref: ../../../../components/responses/401.yaml#/401