Add pagination to subscriptions feed

[eskbr]

It would be nice if this was added, as of now if you have many subscriptions it lags out and the experience is slow, with pagination (maybe somethig similar to how the channels tabs does it, the experience would be much smoother.

I'm going to see if i can implement something like this myself, but note that i dont have familiarity with the language.

Nontheless thank you for creating an amazing piece of software!

[migalmoreno]

Yeah, I haven't implemented pagination for any API-facing functionality yet, and I definitely can see how the current feed implementation would become laggy with many subs. Local data persistence (IndexedDB) serialization for the feed items in the FE could also be making the problem worse, since as storage grows the write times are increasing significantly, which I'll have to tackle some time soon by offloading all persistence to a separate thread to prevent it blocking the DOM.

Even though for other pages like bookmarks pagination is easier to implement since we can simply retrieve N items from the DB, I'm not yet sure how we could pre-filter the number of feed items that we retrieve for all channels, as the current bottleneck is here. I'd be happy to hear suggestions for this if someone has any.

I've also thought about implementing a PubSub mechanism to automate and optimize the feed retrieval but I haven't gotten to it yet, as I'm not sure it can be applied to all services.