Add a timestamp field to TopUpEvent and StreamTransferEvent for event-shape consistency

[Austinaminu2]

Description

Every other stream lifecycle event (`StreamCreatedEvent`, `WithdrawEvent`, `CancelEvent`, `StreamBumpedEvent`, pause/unpause events) carries a `timestamp` field, but `TopUpEvent` and `StreamTransferEvent` (`lib.rs:234-247`) don't — breaking event-shape consistency for anyone indexing these events.

Task

Add a `timestamp` field to both event structs, populated the same way the other lifecycle events populate theirs, and update the corresponding emit call sites and any tests asserting on event shape.

Good for contributors because

Clear, well-scoped consistency fix with an existing pattern (the other event structs) to copy from.

[BIGSMKE12]

@BIGSMKE12 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello Maintainer, I’ve inspected the issue details and understand the intended result. I’d appreciate the chance to implement the fix.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @BIGSMKE12 to this issue.

[OZILSOLAR]

@OZILSOLAR has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

OZILSOLAR
Hi team!!!!
I came across this issue and would love to work on it. I have experience with similar tasks and I'm confident I can investigate, implement a clean solution, and thoroughly test it before submitting a PR. If the issue is still open, I would appreciate it if you could assign it to me. Thank you!!!!!!

ℹ️ Repo Maintainers: To accept this application, review their application or assign @OZILSOLAR to this issue.

[escaprt]

@escaprt has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I’d like to work on Issue #662 because TopUpEvent and StreamTransferEvent are the only stream lifecycle events that do not currently include a timestamp. This makes the event shapes inconsistent and creates unnecessary work for indexers that need a common way to order and process lifecycle events.

I will first review the existing event structs in lib.rs and compare them with StreamCreatedEvent, WithdrawEvent, CancelEvent, StreamBumpedEvent, and the pause/unpause events to follow the project's established timestamp pattern.

I will then add a timestamp field to both TopUpEvent and StreamTransferEvent and populate it using the same source and approach already used by the other lifecycle events.

I will update every relevant event emission call site so the new field is always included correctly, without changing the existing event data or behavior.

I will also review the current tests and update or add assertions covering the new event shape and timestamp values. The tests will verify that both events emit the timestamp consistently with the other stream lifecycle events.

Finally, I will run the relevant contract tests and build checks to confirm the changes compile cleanly and that existing event behavior remains intact.

My goal is to make the stream event schema consistent across all lifecycle events, giving indexers a reliable timestamp field for TopUpEvent and StreamTransferEvent without introducing unnecessary changes.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @escaprt to this issue.

[Kappa16]

@Kappa16 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi, I'd like to take this on.
I understand what's being asked here and I'm confident I can implement an accurate fix correctly and efficiently.
I'd appreciate being assigned to this issue and look forward to contributing.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Kappa16 to this issue.

[drips-wave]

Congratulations, @OZILSOLAR! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @OZILSOLAR: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Third Campaign campaign!

@OZILSOLAR's PR #708 was approved and merged by @Austinaminu2.

🏆 @OZILSOLAR: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (923 total points). Track your full progress on GrantFox.

👏 Great work, @OZILSOLAR! Keep contributing to FlowwStar.

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This issue has been completed by @OZILSOLAR as part of the Stellar Wave Program's 8th Wave 🥳

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