Add an extend-only entrypoint to lengthen the funding deadline while the escrow is open

[mikewheeleer]

Add an extend-only entrypoint to lengthen the funding deadline while the escrow is open

Description

The escrow exposes get_funding_deadline and is_funding_expired, and an under-funded escrow becomes cancellable once the deadline lapses. However, there is no admin path to push the deadline out when an SME needs more time to attract investors — the only options today are to let it expire or cancel and re-deploy. This forces a destructive teardown for what should be a routine schedule adjustment.

This issue adds an extend_funding_deadline(new_deadline) admin entrypoint that may only move the deadline forward (never shorten it), is gated to the open funding window, and emits a structured event so integrators can re-sync their off-chain timers.

Requirements and context

• Repository scope: Liquifact/Liquifact-contracts only.
• Add extend_funding_deadline(new_deadline: u64) gated by admin require_auth via the existing admin loader, callable only while the escrow status is open (not funded, settled, or cancelled).
• Reject any new_deadline that is less than or equal to the current stored deadline with a new typed EscrowError variant (e.g. FundingDeadlineNotExtended), keeping error codes append-only.
• Respect the maturity bound: reject a new_deadline at or beyond the maturity timestamp so the funding window cannot swallow settlement.
• Emit a structured event carrying invoice_id, the old deadline, and the new deadline.
• Bump the persistent/instance TTL for any touched entry.

Suggested execution

• Fork the repo and create a branch
• git checkout -b feature/contracts-extend-funding-deadline
• Implement changes
  • Write code in: escrow/src/lib.rs — extend_funding_deadline, the new typed error, and the deadline-extended event struct.
  • Write comprehensive tests in: escrow/src/tests/funding.rs — assert forward-only moves, rejection of equal/earlier deadlines, the maturity-bound guard, the status gate, admin auth, and the emitted event payload.
  • Add documentation: update README.md and the funding-lifecycle docs to describe deadline extension and its bounds.
  • Include NatSpec-style doc comments (///) on the new entrypoint, matching the existing style in lib.rs.
  • Validate security assumptions: no shortening, no extension past maturity, admin-only, correct status gating.
• Test and commit

Test and commit

• Run cargo fmt --all -- --check, cargo build, and cargo test.
• Cover edge cases and failure paths: equal deadline, earlier deadline, deadline past maturity, non-admin caller, funded/settled/cancelled status.
• Include the full cargo test output and a short security notes section in the PR description.

Example commit message

feat: add extend-only funding deadline entrypoint with bounds, event, tests and docs

Guidelines

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

Community & contribution rewards

• 💬 Join the Liquifact community on Discord for questions, reviews, and faster merges: https://discord.gg/JrGPH4V3
• ⭐ 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.