[MM-21919] Add use_channel_mentions permission (#13781)

* MM-21919 Add channel_mention permission

* MM-21919 Fix emojis migration test

* Enforce Channel Mentions on the in the posts api

* MM-21919 Rename permission to use_channel_mentions

Allow posts with channel mentions to still be posted without the permission just don't send notifications to users

* MM-21919 Add tests for a post with @all and @here

* MM-21919 Add use channel mentions to all roles that have create post

* MM-21919 Update app_test to include use_channel_mentions permission in default permissions

app/notification_test.go

@@ -876,47 +876,37 @@ func TestGetExplicitMentionsAtHere(t *testing.T) {
 }
 
 func TestAllowChannelMentions(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	post := &model.Post{ChannelId: th.BasicChannel.Id, UserId: th.BasicUser.Id}
+
 	t.Run("should return true for a regular post with few channel members", func(t *testing.T) {
-		th := Setup(t)
-		defer th.TearDown()
-
-		post := &model.Post{}
-
 		allowChannelMentions := th.App.allowChannelMentions(post, 5)
-
 		assert.True(t, allowChannelMentions)
 	})
 
 	t.Run("should return false for a channel header post", func(t *testing.T) {
-		th := Setup(t)
-		defer th.TearDown()
-
-		post := &model.Post{Type: model.POST_HEADER_CHANGE}
-
-		allowChannelMentions := th.App.allowChannelMentions(post, 5)
-
+		headerChangePost := &model.Post{ChannelId: th.BasicChannel.Id, UserId: th.BasicUser.Id, Type: model.POST_HEADER_CHANGE}
+		allowChannelMentions := th.App.allowChannelMentions(headerChangePost, 5)
 		assert.False(t, allowChannelMentions)
 	})
 
 	t.Run("should return false for a channel purpose post", func(t *testing.T) {
-		th := Setup(t)
-		defer th.TearDown()
-
-		post := &model.Post{Type: model.POST_PURPOSE_CHANGE}
-
-		allowChannelMentions := th.App.allowChannelMentions(post, 5)
-
+		purposeChangePost := &model.Post{ChannelId: th.BasicChannel.Id, UserId: th.BasicUser.Id, Type: model.POST_PURPOSE_CHANGE}
+		allowChannelMentions := th.App.allowChannelMentions(purposeChangePost, 5)
 		assert.False(t, allowChannelMentions)
 	})
 
 	t.Run("should return false for a regular post with many channel members", func(t *testing.T) {
-		th := Setup(t)
-		defer th.TearDown()
-
-		post := &model.Post{}
-
 		allowChannelMentions := th.App.allowChannelMentions(post, int(*th.App.Config().TeamSettings.MaxNotificationsPerChannel)+1)
+		assert.False(t, allowChannelMentions)
+	})
 
+	t.Run("should return false for a post where the post user does not have USE_CHANNEL_MENTIONS permission", func(t *testing.T) {
+		defer th.AddPermissionToRole(model.PERMISSION_USE_CHANNEL_MENTIONS.Id, model.CHANNEL_USER_ROLE_ID)
+		th.RemovePermissionFromRole(model.PERMISSION_USE_CHANNEL_MENTIONS.Id, model.CHANNEL_USER_ROLE_ID)
+		allowChannelMentions := th.App.allowChannelMentions(post, 5)
 		assert.False(t, allowChannelMentions)
 	})
 }