Avoid counting top channel posts for posts made by plugins and OAuth apps (#20943)

* add from_integration prop to oauth posts to:
- oauth app posts
- plugin posts
- slash command responses
- incoming webhook posts

* tests

* include check for bot posts

* use from_plugin and from_oauth_app props

* fix test

* avoid counting top channel posts for posts made by plugins and oauth apps

app/plugin_api_test.go

@@ -1383,6 +1383,25 @@ func TestPluginCreatePostWithUploadedFile(t *testing.T) {
 	assert.Equal(t, model.StringArray{fileInfo.Id}, actualPost.FileIds)
 }
 
+func TestPluginCreatePostAddsFromPluginProp(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+	api := th.SetupPluginAPI()
+
+	channelID := th.BasicChannel.Id
+	userID := th.BasicUser.Id
+	post, err := api.CreatePost(&model.Post{
+		Message:   "test",
+		ChannelId: channelID,
+		UserId:    userID,
+	})
+	require.Nil(t, err)
+
+	actualPost, err := api.GetPost(post.Id)
+	require.Nil(t, err)
+	assert.Equal(t, "true", actualPost.GetProp("from_plugin"))
+}
+
 func TestPluginAPIGetConfig(t *testing.T) {
 	th := Setup(t)
 	defer th.TearDown()