Fix empty home sections

[flofriday]

Description

Previously sections on the homescreen sometimes didn't contain any content if for example there weren't no downloads. Now only sections with useful information will be shown, which should be much cleaner for new users, which haven't listened to anything yet.

As a techical detail, the sections don't get removed from the homescreen but just hide them self. This way they can still be listening to updates and just need to unhide themself if new relevant podcasts/episodes appear.

Screenshot (left before, right this PR):

Checklist

• I have read the contribution guidelines: https://github.com/AntennaPod/AntennaPod/blob/develop/CONTRIBUTING.md#submit-a-pull-request
• I have performed a self-review of my code
• I have run the automated code checks using ./gradlew checkstyle spotbugsPlayDebug spotbugsDebug :app:lintPlayDebug
• My code follows the style guidelines of the AntennaPod project: https://github.com/AntennaPod/AntennaPod/wiki/Code-style
• I have mentioned the corresponding issue and the relevant keyword (e.g., "Closes: #xy") in the description (see https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue)
• If it is a core feature, I have added automated tests

[loucasal]

This is one of the suggestions I made in #6824, so great to see it picked up. See that ticket for some closely related ideas (all still to be tackled).

[flofriday]

You are right, I musst have missed it but your issue contains even more suggestions we could work on ;)

[keunes]

Super that you worked on this (and all the other stuff)! I just added the 'Needs: Decision' label because I'm not sure of we want to hide them all if empty, because it also limits discoverability of the sections. Also this could lead to unexpected behaviour where you enable/activate a section but it doesn't show, because no content is available

Another option that doesn't have these downsides is an 'empty state' screen. Like a simple graphic to go with a short note.

If not for all sections, then maybe for some (e.g. more important for Queue than for Inbox).

[flofriday]

No problem at all, just displaying an empty message instead of hiding the section should be an easy fix and could be the better solution since the sections can be disabled (which I kinda forgot).

[keunes]

Discussed with @ByteHamster:

• we will want to keep Queue to encourage users to add content. So those we'd already keep.
• For the Inbox it's a bit unexpected for the inbox to disappear
• Subscriptions will always have something (there is a full empty state screen if you don't have subscriptions yet)
• if you're a user gradually starting to use AP, then some sections might start appearing & disappearing

So we prefer to have 'empty state' for all.

We considered having something like the 'loading' placeholder images (with text on top), but that would get too busy:

So we decided to go for only texts right now, in future to be complemented with a nice empty-state image (to be designed by a designer). Text would be vertically & horizontally centred (but with smaller margins). We'll create dedicated strings (we'll think about the exact text in the coming time). The existing texts come out a bit too long (a GIMP mock-up):