api: Add go files

I know this is a huge commit, but I can't be bothered to check
this in part by part.

api/commenter_session.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"time"
+)
+
+type commenterSession struct {
+	Session      string    `json:"session"`
+	CommenterHex string    `json:"commenterHex"`
+	CreationDate time.Time `json:"creationDate"`
+}