Add SubscribeForAddress explorer API (#507)

* Add SubscribeForAddress explorer API

* Add SubscribeForAddress to SDK transport client

* Fixes

* Force close all open connections at shutdown

* Add method to notify for incoming funds to the SDK

* Fixes

Author: altafan

api-spec/openapi/swagger/ark/v1/explorer.swagger.json

@@ -105,6 +105,45 @@
           "ExplorerService"
         ]
       }
+    },
+    "/v1/vtxos/{address}/subscribe": {
+      "get": {
+        "operationId": "ExplorerService_SubscribeForAddress",
+        "responses": {
+          "200": {
+            "description": "A successful response.(streaming responses)",
+            "schema": {
+              "type": "object",
+              "properties": {
+                "result": {
+                  "$ref": "#/definitions/v1SubscribeForAddressResponse"
+                },
+                "error": {
+                  "$ref": "#/definitions/rpcStatus"
+                }
+              },
+              "title": "Stream result of v1SubscribeForAddressResponse"
+            }
+          },
+          "default": {
+            "description": "An unexpected error response.",
+            "schema": {
+              "$ref": "#/definitions/rpcStatus"
+            }
+          }
+        },
+        "parameters": [
+          {
+            "name": "address",
+            "in": "path",
+            "required": true,
+            "type": "string"
+          }
+        ],
+        "tags": [
+          "ExplorerService"
+        ]
+      }
     }
   },
   "definitions": {
@@ -242,6 +281,25 @@
       ],
       "default": "ROUND_STAGE_UNSPECIFIED"
     },
+    "v1SubscribeForAddressResponse": {
+      "type": "object",
+      "properties": {
+        "newVtxos": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "$ref": "#/definitions/v1Vtxo"
+          }
+        },
+        "spentVtxos": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "$ref": "#/definitions/v1Vtxo"
+          }
+        }
+      }
+    },
     "v1Tree": {
       "type": "object",
       "properties": {

api-spec/protobuf/ark/v1/explorer.proto

@@ -21,6 +21,11 @@ service ExplorerService {
       get: "/v1/vtxos/{address}"
     };
   };
+  rpc SubscribeForAddress(SubscribeForAddressRequest) returns (stream SubscribeForAddressResponse) {
+    option (google.api.http) = {
+      get: "/v1/vtxos/{address}/subscribe"
+    };
+  };
 }
 
 message GetRoundRequest {
@@ -44,3 +49,11 @@ message ListVtxosResponse {
   repeated Vtxo spendable_vtxos = 1;
   repeated Vtxo spent_vtxos = 2;
 }
+
+message SubscribeForAddressRequest {
+  string address = 1;
+}
+message SubscribeForAddressResponse {
+  repeated Vtxo new_vtxos = 2;
+  repeated Vtxo spent_vtxos = 3;
+}