/v2/items: Add flag for Research Kit salvage

[Keorl]

Feature Description

There is already a NoSalvage flag, but the api doesn't have the separate flag for salvage with Research Kit.

Given that this flag is now fairly inconsistent (contrarily to its release description : anything that is crafted) and can change with each patch, having it in the API would let community tools provide lists of items that can be salvaged for Research Pages.
Also, it would be great to have the research loot table for each item where applicable. It would make it possible to calculate possible returns at any given time. Again, it changes with patches and there are thousands and thousands of items so community research can simply not follow.
Together, those API changes would make it possible to provide tools for players who need research pages (cheapest ways, best ways to use your current materials ...), and would drastically ease the very bad perception of this new system.
Combined with the 2022-10-04 patch, Research system would finally be what it aims to be : a good general sink for materials. It would then be possible to balance returns, and also revert the change on legendary skins (2.5 -> 10k notes) as notes wouldn't be annoying to get anymore and we need long term big sinks for them to play their role in the game's economy.

Note : I posted this months ago there : arenanet/api-cdi#684. And I was only now informed by someone that you have a new repo. I don't have a clue why, but you should at least have a big warning on the old one and a link to this one.

Implementation

endpoint : /v2/items/:id
add property : Researchable
add property : ResearchAverageNotes

Example

No response

Anything else?

No response