Add optional funding target to escrow (#144)

README.md

@@ -145,7 +145,7 @@ Core single-issue bounty escrow.
 
 ```rust
 fn initialize(env, admin: Address, treasury: Address, fee_bps: u32) -> Result<(), Error>;
-fn fund(env, issue_id: u64, sponsor: Address, token: Address, amount: i128, deadline: u64) -> Result<(), Error>;
+fn fund(env, issue_id: u64, sponsor: Address, token: Address, amount: i128, deadline: u64, target: Option<i128>) -> Result<(), Error>;
 fn contribute(env, issue_id: u64, sponsor: Address, amount: i128) -> Result<(), Error>;
 fn release(env, issue_id: u64, recipients: Vec<(Address, u32)>) -> Result<(), Error>;
 fn refund(env, issue_id: u64) -> Result<(), Error>;
@@ -159,10 +159,12 @@ fn get_fee_bps(env) -> Result<u32, Error>;
 ```
 
 - `fund`: `sponsor.require_auth()`. Transfers `amount` of `token` from the
-  sponsor into the contract and *creates* the escrow. One escrow per
-  `issue_id` — a second `fund` call on the same id is rejected
-  (`AlreadyFunded`); every sponsor after the first uses `contribute`
-  instead.
+  sponsor into the contract and *creates* the escrow. `target` is an
+  optional funding goal stored on the escrow and read-only thereafter —
+  informational only, so it does not block `contribute` past it and does not
+  change `release`/`refund` behavior. One escrow per `issue_id` — a second
+  `fund` call on the same id is rejected (`AlreadyFunded`); every sponsor
+  after the first uses `contribute` instead.
 - `contribute`: `sponsor.require_auth()`. Adds an additional sponsor's
   funds to an already-`fund`ed escrow — this is how crowdfunding a single
   `issue_id` across several sponsors works. Uses the token already

contracts/escrow/src/lib.rs

@@ -71,10 +71,13 @@ impl EscrowContract {
     /// Sponsor deposits `amount` of `token` into escrow for `issue_id`,
     /// creating it. Requires the sponsor's authorization. `deadline` is a
     /// unix timestamp (ledger time) after which, if unpaid, contributors
-    /// may reclaim their funds. One escrow per `issue_id` — a second `fund`
-    /// call on the same id is rejected (`AlreadyFunded`); every sponsor
-    /// after the first uses `contribute` instead. See
-    /// `docs/escrow-crowdfunding-design.md` for why creation and
+    /// may reclaim their funds. `target` is an optional funding goal that is
+    /// stored verbatim and never mutated afterward — it is informational
+    /// only, so it does not block `contribute` from pushing `amount` past it
+    /// and does not change `release`/`refund` behavior. One escrow per
+    /// `issue_id` — a second `fund` call on the same id is rejected
+    /// (`AlreadyFunded`); every sponsor after the first uses `contribute`
+    /// instead. See `docs/escrow-crowdfunding-design.md` for why creation and
     /// contribution are kept as two separate entrypoints.
     ///
     /// Note: this contract has no visibility into `mergefi-milestones` —
@@ -90,6 +93,7 @@ impl EscrowContract {
         token: Address,
         amount: i128,
         deadline: u64,
+        target: Option<i128>,
     ) -> Result<(), Error> {
         sponsor.require_auth();
 
@@ -114,6 +118,7 @@ impl EscrowContract {
         let escrow = Escrow {
             token,
             amount,
+            target,
             status: EscrowStatus::Funded,
             created_at: env.ledger().timestamp(),
             deadline,