Add Loadout Items ADR

[erri120]

Also fixes the count on the loadout card.

Part of #1763.

[Sewer56]

This works for me, but I'll leave it for @halgari and @Al12rs to add any addendums they wish to.

Previous Resources:

• Loadout Items ADR #1680 (Old Design. Not used)
• Initial Loadout Items #1750 (More Detailed Diagram)

[Sewer56]

I think what would help in understanding, is also giving an example of how a conventional 'mod' is represented with the new system.

I wasn't involved in original planning of LoadoutItems, but with the current system, as I understand it given around 1.5 hours of poking around for GC stuff:

• Each file is a LoadoutFile -> LoadoutItemWithTargetPath -> LoadoutItem (arrow meaning inheritance)
• An installed archive (formerly 'Mod') is a LoadoutItemGroup which does not contain a parent.
  • Each file from that archive has the LoadoutItemGroup set as the parent.
  • Any file with custom metadata should extend LoadoutFile, and contain a custom marker.
  • Any group (e.g. type of mod, RedMod etc.) should extend LoadoutItemGroup with custom marker.
• Items are stored in library by linking a LoadoutItemGroup with a LibraryItem in what's essentially a join table. (Edit: Entries of these tables are themselves LoadoutItems)

This works for me, but these kinds of relationships should be stated clearly somewhere in dev docs; in order to try better document the system.

[Sewer56]

Aah, this also needs to update mkdocs.yml.