add support for modified hex stream requests

src/service/mobile_config.proto

@@ -221,6 +221,18 @@ message boosted_hex_info_stream_req_v1 {
   bytes signature = 3;
 }
 
+message boosted_hex_modified_info_stream_req_v1 {
+  // max number of boosted hex info records in each message of the response
+  // stream
+  uint32 batch_size = 1;
+  // return only those records which were modified after the specified timestamp
+  // unix epoch timestamp in seconds
+  uint64 timestamp = 2;
+  // pubkey binary of the signing keypair
+  bytes signer = 3;
+  bytes signature = 4;
+}
+
 message boosted_hex_info_stream_res_v1 {
   // a list of boosted hex info
   repeated boosted_hex_info_v1 hexes = 1;
@@ -279,4 +291,7 @@ service hex_boosting {
   // Get a stream of hex boost info
   rpc info_stream(boosted_hex_info_stream_req_v1)
       returns (stream boosted_hex_info_stream_res_v1);
+  // Get a stream of modified hex boost info since the specified timestamp
+  rpc modified_info_stream(boosted_hex_modified_info_stream_req_v1)
+      returns (stream boosted_hex_info_stream_res_v1);
 }