Group Tasks Shared Completion (#10515)

* WIP(groups): add shared completion prop
Also fix an issue where the Needs Approval toggle would not read/save 
correctly.

* fix(groups): save group options on task create
Also, correct count of assigned members when viewing user is among 
assignments

* fix(groups): display correct messages in two places

* fix(tasks): eliminate console error related to filtering
Also localize a group plans string

* WIP(groups): implement single completion for approval workflow

* WIP(groups): Add shared completion handling to no-approval-needed flow

* WIP(groups): cover approval flow case for all-assigned
Also save new field on initial task creation

* fix(tasks): use default sharedCompletion value when creating tasks

* WIP(tests): non-working draft test

* Added completed todo to group query

* WIP(group-tasks): fix bugs, add tests

* refactor(group-tasks): deleteMany op, add more tests

* refactor(group-tasks): move shared completion handling to lib

* WIP(group-tasks): broken refactor

* WIP(group-tasks): await all the things

* Turned complete master task to save

* WIP(group-tasks): show completed

* fix(filtering): don't try to filter if no list is passed

* refactor(group-tasks): load completed to-dos on demand, not at start

* fix(group-tasks): don't double up on repeat visits

* fix(group-tasks): include brief explanation in dropdown

* fix(group-tasks): improve wording some more

website/server/libs/taskManager.js

@@ -3,6 +3,9 @@ import * as Tasks from '../models/task';
 import {
   BadRequest,
 } from './errors';
+import {
+  SHARED_COMPLETION,
+} from './groupTasks';
 import _ from 'lodash';
 import shared from '../../common';
 
@@ -96,6 +99,7 @@ export async function createTasks (req, res, options = {}) {
       if (taskData.requiresApproval) {
         newTask.group.approval.required = true;
       }
+      newTask.group.sharedCompletion = taskData.sharedCompletion || SHARED_COMPLETION.default;
     } else {
       newTask.userId = user._id;
     }
@@ -183,11 +187,12 @@ export async function getTasks (req, res, options = {}) {
         limit = 0; // no limit
       }
 
-      query = {
-        userId: user._id,
-        type: 'todo',
-        completed: true,
-      };
+      query.type = 'todo';
+      query.completed = true;
+
+      if (owner._id === user._id) {
+        query.userId = user._id;
+      }
 
       sort = {
         dateCompleted: -1,