/feed and /new with an additional filter on tag

[tibfox]

There should be additional endpoints for /feed and /new to filter on a tag.

There is the plan to implement a story/shorts feature inside of the app. For that I will need a new endpoint on the api level to load posts from followings with a specific tag included. ( I would suggest "moments" but making it dynamic is probably the best choice)

The same would be good to have for the /new endpoint. That way we could implement tag lists.

@skzap already had this idea:
3. is pretty easy to do honestly, just copy paste the /feed endpoint and add the filter by tag in the mongo query

[tibfox]

I would append that item with: filter by tags just a comma separated list to check posts with tags in the range of this list.

[tibfox]

brish wanna work in that