Add COSMIC category to appstream metainfo

[jackpot51]

This will allow it to show up in a COSMIC-specific page in the COSMIC store. pop-os/cosmic-store#167

[mariinkys]

Perfect, thank you!

[bbhtt]

Appstream hasn't updated its category list, so having this now will make it fail validation.

Also it filters all DE names as low quality categories. When the category list in appstream is updated, you have to ask the appstream maintainer to not filter it if you want it in the appstream catalogue data.

See https://github.com/ximion/appstream/blob/3203d61a6bdd248ae4045e13f00cf0951786151c/src/as-utils.c#L1337

[jackpot51]

I don't see that mattering for the use case since cosmic-store does its own appstream parsing.

[bbhtt]

Are you parsing the metainfo files directly or the composed catalogue data?

If it's the latter, and the COSMIC category is filtered by appstream even if you have it in metainfo it will not be present in the catalogue data.

[jackpot51]

Parsing the composed metainfo. I will request it is not filtered out.

ximion/appstream#669

[jackpot51]

@mariinkys I will consult more with @ximion, but for now I'd recommend to remove the COSMIC category and set project_group to COSMIC instead.

[jackpot51]

We are comsidering the following, verbatim, for identifying apps made for COSMIC, as discussed on the Pop Chat https://chat.pop-os.org/pop-os/pl/izo1y3d9rtrttyryji7yfnxyoh

For an app:

<provides>
    <id>com.system76.CosmicApplication</id>
</provides>

For an applet:

<provides>
    <id>com.system76.CosmicApplet</id>
</provides>