Support Multiple Payment Tokens

[Bosun-Josh121]

Target Contract: payment-vault-contract
Labels: phase-1-vault, feature

Description: Currently fixed to one token at init. The platform should support XLM, USDC, and other stablecoins simultaneously.

Tasks:

• src/storage.rs: Replace single DataKey::Token with DataKey::AllowedToken(Address) -> bool. Add add_allowed_token and remove_allowed_token helpers.
• src/types.rs: Add token_address: Address to BookingRecord.
• src/contract.rs: Implement add_payment_token(env, token). Admin auth required. Update book_session to accept payment_token: Address. Verify storage::is_token_allowed(payment_token).
• src/lib.rs: Expose pub fn add_payment_token(env: Env, token: Address) and update book_session signature in #[contractimpl].
• src/test.rs: Admin adds USDC. User books with USDC -> Success. User books with unregistered fake token -> Fails.

Acceptance Criteria:

• Users can book sessions using different whitelisted assets.

[MethelyDev]

@MethelyDev has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I would like to work on this issue, kindly assign me

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[oscar24357]

@oscar24357 has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

i would like to work on this issue, kindly assign me to it, thank you

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[Ultra-Tech-code]

@Ultra-Tech-code has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Hello, I can work on this issue.

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[EmmyKay0026]

@EmmyKay0026 has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hi @LightForgeHub, I’m interested! Transitioning from a single-asset model to a multi-token architecture is a significant upgrade for the platform's utility and flexibility.

I’ll refactor the storage layer to use a mapping for allowed tokens and update the BookingRecord to track the specific asset used for each transaction. I’ll also implement the admin-guarded whitelist management and ensure book_session strictly validates the incoming payment_token address against our storage. Should the add_payment_token function also include a "price feed" parameter if we ever need to normalize different tokens to a base USD value, or is simple whitelisting sufficient for now?

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