Added adoption report and transfer code

docs/API_REFERENCE.md

@@ -897,6 +897,40 @@ Possible errors:
 - `409` if that owner email owns more than one receiving flock
 - `409` if the destination flock already has a bird using the same `tagId`
 
+#### `POST /api/birds/:birdId/transfer-code`
+
+Requires a browser session, write access, and role `owner` or `assistant`. Creates a unique transfer code for a bird. Creating a new open code for the same bird revokes earlier unused codes for that bird.
+
+Response `201`:
+
+```json
+{
+  "transferCode": {
+    "code": "secure-code",
+    "bird": {}
+  }
+}
+```
+
+#### `POST /api/bird-transfer-codes/:code/accept`
+
+Requires a browser session, write access, and role `owner` or `assistant`. Accepts a transfer code into the signed-in user's active flock.
+
+Response `200`:
+
+```json
+{
+  "bird": {},
+  "sourceWorkspaceName": "Previous Flock",
+  "workspace": {}
+}
+```
+
+Possible errors:
+
+- `404` if the code does not exist, was revoked, was already used, or the bird is no longer available
+- `409` if the bird is already in the active flock or the active flock already has the same `tagId`
+
 #### `DELETE /api/birds/:birdId`
 
 Requires auth with write access and role `owner`, `assistant`, or `caregiver`. Deletes a bird.