test: add RPC call to PegIn integration test, document new RPC endpoint

docs/rpc/openapi.yaml

@@ -39,7 +39,20 @@ paths:
                 $ref: ./api/transaction/post-core-node-transactions-error.schema.json
               example:
                 $ref: ./api/transaction/post-core-node-transactions-error.example.json
-
+  /v2/burn_ops/{burn_height}/{op_type}:
+    get:
+      summary: Get burn operations
+      description: Get all burn operations of type `op_type` successfully read at `burn_height`. Valid `op_type`s are just `peg_in` for now.
+      tags:
+        - Info
+      operationId: get_burn_ops
+      responses:
+        200:
+          description: Burn operations list
+          content:
+            application/json:
+              example:
+                $ref: ./api/core-node/get-burn-ops.example.json
   /v2/contracts/interface/{contract_address}/{contract_name}:
     get:
       summary: Get contract interface