add support GetMultipleKeys

Signed-off-by: Fedor Partanskiy <fredprtnsk@gmail.com>

peer/chaincode.proto

@@ -131,4 +131,6 @@ message ChaincodeData {
 message ChaincodeAdditionalParams {
     bool use_write_batch = 1; // an indication that the peer can handle state write batches
     uint32 max_size_write_batch = 2; // maximum size of batches with write state
+    bool use_get_multiple_keys = 3; // an indication that the peer can handle get multiple keys
+    uint32 max_size_get_multiple_keys = 4; // maximum size of batches with get multiple keys
 }

peer/chaincode_shim.proto

@@ -39,6 +39,7 @@ message ChaincodeMessage {
         GET_PRIVATE_DATA_HASH = 22;
         PURGE_PRIVATE_DATA = 23;
         WRITE_BATCH_STATE = 24;
+        GET_STATE_MULTIPLE = 25;
     }
 
     Type type = 1;
@@ -73,6 +74,20 @@ message GetStateMetadata {
     string collection = 2;
 }
 
+// GetStateMultiple is the payload of the ChaincodeMessage.
+// It contains the keys to be retrieved from the ledger.
+// If a collection is specified, the keys will be retrieved
+// from the collection (i.e., the private state).
+message GetStateMultiple {
+    repeated string keys = 1;
+    string collection = 2;
+}
+
+// GetStateMultipleResult is result of executing the GetStateMiltiple request
+message GetStateMultipleResult {
+    repeated bytes values = 1;
+}
+
 // PutState is the payload of a ChaincodeMessage. It contains a key and value
 // which needs to be written to the transaction's write set. If the collection is
 // specified, the key and value would be written to the transaction's private