feat: Add server-only purchasing mode to GameProductService

[unrooot]

By default a client can prompt a purchase for any asset id via GameProductServiceClient:PromisePromptPurchase. When selling limited UGC this lets an exploiter prompt arbitrary asset ids. Enabling server-only prompting makes the client reject local prompts so that prompts must be initiated from the server, where you can validate the asset id:

-- Server
local gameProductService = serviceBag:GetService(require("GameProductService"))
gameProductService:SetServerOnlyPromptingEnabled(true)

-- Now prompt from the server (validate idOrKey first), e.g.
gameProductService:PromisePlayerPromptPurchase(player, GameConfigAssetTypes.ASSET, assetId)

On the client, GameProductServiceClient:PromisePromptPurchase rejects while this mode is enabled. Use GameProductServiceClient:ObserveServerOnlyPromptingEnabled() to hide or disable buy buttons.

Note: this prevents the helper API from prompting arbitrary ids; a client can still call Roblox's MarketplaceService:PromptPurchase directly, so server-side validation of what you sell remains the real authority.

[github-actions]

Deploy Results

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Test Results

Package	Status	Try it
@quenty/gameproductservice	✅ Passed (927ms)	Open | Play

1 tested, 1 passed, 0 failed in 6.3s · View logs