feat(app): ✨ inbox post command placehoder

greataped/app/commands/spi/post_to_inbox.go

@@ -0,0 +1,10 @@
+package spi
+
+import (
+	. "rail.town/infrastructure/components/constants"
+	. "rail.town/infrastructure/components/contracts"
+)
+
+func PostToInbox(x IDispatcher, username string) (IPostToInboxResult, error) {
+	return nil, ERROR_NOT_IMPLEMENTED
+}