[Contract] Build Asset Leasing Module

[yusuftomilola]

Enables an asset owner (lessor) to lease an asset to a lessee for a defined period with rent terms tracked on-chain.

Requirements

Lease struct: lease_id: BytesN<32>, asset_id: BytesN<32>, lessor: Address, lessee: Address, start_timestamp: u64, end_timestamp: u64, rent_per_period: i128, deposit: i128, status: LeaseStatus (Active, Returned, Cancelled, Expired)

Functions:

• create_lease(env, asset_id, lease_id, lessor, lessee, start, end, rent, deposit) — lessor authenticates; asset must not already have an active lease; stores lease and updates asset active lease index; emits event
• return_leased_asset(env, lease_id, caller) — lessor or lessee; sets status to Returned; clears active lease index
• cancel_lease(env, lease_id, caller) — lessor only; only before start_timestamp
• expire_lease(env, lease_id) — permissionless; only if end_timestamp < now; sets Expired
• get_lease(env, lease_id)
• get_asset_active_lease(env, asset_id) — returns Option<BytesN<32>>
• get_lessee_leases(env, lessee) — index of all lease IDs for a lessee

Acceptance Criteria

• Creating a lease on an already-leased asset fails
• cancel_lease fails after the lease start timestamp
• Lessee index updated on creation