Add remove_service_price to clear a configured price and revert a service to free

[mikewheeleer]

Implement a price-removal entrypoint for services

Description

set_service_price in contracts/escrow/src/lib.rs can write or overwrite a price under DataKey::ServicePrice(service_id), but there is no way to remove the entry — the only way to make a previously-priced service free again is to write 0, which leaves a dangling stored key paying ledger rent and is semantically ambiguous (an explicit zero price vs. no price configured both read back as 0 from get_service_price). This issue adds an explicit removal entrypoint so operators can fully retire a price.

Requirements and context

• Repository scope: Agentpay-Org/Agentpay-contracts only.
• Add remove_service_price(env, service_id): admin-gated via the existing Admin + require_auth() pattern, calling env.storage().persistent().remove(&DataKey::ServicePrice(service_id)). Idempotent — removing an absent price is a no-op.
• Document that after removal get_service_price and compute_billing read back as the 0 default, identical to a never-priced service.
• Emit a price_removed(service_id) event (additive) so indexers can distinguish a removal from a set to zero.
• Honour the pause gate consistently with the other admin mutations.

Suggested execution

• Fork the repo and create a branch
• git checkout -b feature/contracts-remove-service-price
• Implement changes
  • Write code in: contracts/escrow/src/lib.rs — remove_service_price entrypoint + event.
  • Write comprehensive tests in: contracts/escrow/src/test.rs — set then remove returns get_service_price == 0; remove on never-priced service is a no-op; non-admin caller panics; event fires.
  • Add documentation: clarify the zero-vs-removed distinction in README.md.
  • Include NatSpec-style doc comments (///) matching the existing style in lib.rs.
  • Validate security: only admin can remove, no fund/billing inconsistency after removal.
• Test and commit

Test and commit

• Run cargo fmt --all -- --check, cargo build, and cargo test.
• Cover edge cases: remove then re-set, remove an unregistered service's price, compute_billing after removal.
• Include the full cargo test output and a short security notes section in the PR description.

Example commit message

feat: add remove_service_price to clear a configured service price

Guidelines

• Minimum 95 percent test coverage for impacted modules.
• Clear, reviewer-focused documentation.
• Timeframe: 96 hours.

Community & contribution rewards

• 💬 Join the AgentPay community on Discord for questions, reviews, and faster merges: https://discord.gg/eXvRKkgcv
• ⭐ This is a GrantFox OSS / Official Campaign task and may be rewarded. When your PR is merged you'll be prompted to rate the project — if this issue and the maintainers helped you ship, we'd be grateful for a 5-star rating. Clear questions in Discord and tidy, well-tested PRs are the fastest path to a merge and a reward.

[Baskarayelu]

I’d love to be assigned this issue and contribute across the relevant areas, whether it involves smart contracts, UI development, backend logic, design implementation, or overall system integration. I’m comfortable working across the full stack and can adapt to the project’s technical requirements to ensure a smooth and consistent contribution.

[grantfox-oss]

🦊 GrantFox — @Baskarayelu has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #35)
2. Your PR will be reviewed by the Agentpay-Org maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

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

@Baskarayelu's PR #65 was approved and merged by @mikewheeleer.

🏆 @Baskarayelu: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (293 total points). Track your full progress on GrantFox.

👏 Great work, @Baskarayelu! Keep contributing to Agentpay-Org.