refactor: move graphql into individual services

app/msgbus/msgbus.graphqls

@@ -0,0 +1,16 @@
+extend type Query {
+    posts(streamID: String! paging: PageInput): Connection!
+}
+extend type Subscription {
+    """after == 0 start from begining, after == -1 start from end"""
+    postAdded(streamID: String! after: Int! = -1): PostEvent
+}
+type PostEvent implements Edge @goModel(model: "github.com/sour-is/ev/app/msgbus.PostEvent") {
+    id: ID!
+
+    payload: String!
+    payloadJSON: Map!
+    tags: [String!]!
+
+    meta: Meta!
+}