Unsubscribe Push (#100)

* add api client with grpc kotlin

* add unsubscribe ability

* update docs

Author: nplasterer

library/src/main/java/org/xmtp/android/library/push/README.md

@@ -79,3 +79,7 @@ This example branch can serve as the basis for what you might want to provide fo
     ```kotlin
     XMTPPush(context, "10.0.2.2:8080").subscribe(conversations.map { it.topic })
     ```
+
+    ```kotlin
+    XMTPPush(context, "10.0.2.2:8080").unsubscribe(conversations.map { it.topic })
+    ```

library/src/main/java/org/xmtp/android/library/push/XMTPPush.kt

@@ -51,6 +51,17 @@ class XMTPPush() {
         client.subscribe(request)
     }
 
+    fun unsubscribe(topics: List<String>) {
+        if (pushServer == "") {
+            throw XMTPException("No push server")
+        }
+        val request = Service.UnsubscribeRequest.newBuilder().also { request ->
+            request.installationId = installationId
+            request.addAllTopics(topics)
+        }.build()
+        client.unsubscribe(request)
+    }
+
     val client: NotificationsGrpc.NotificationsFutureStub
         get() {
             val protocolClient: ManagedChannel =