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_get.go

@@ -0,0 +1,45 @@
+package main
+
+import ()
+
+func commenterGetByHex(commenterHex string) (commenter, error) {
+	if commenterHex == "" {
+		return commenter{}, errorMissingField
+	}
+
+	statement := `
+    SELECT commenterHex, email, name, link, photo, provider, joinDate
+    FROM commenters
+    WHERE commenterHex=$1;
+  `
+	row := db.QueryRow(statement, commenterHex)
+
+	c := commenter{}
+	if err := row.Scan(&c.CommenterHex, &c.Email, &c.Name, &c.Link, &c.Photo, &c.Provider, &c.JoinDate); err != nil {
+		logger.Errorf("error scanning commenter: %v", err)
+		return commenter{}, errorInternal
+	}
+
+	return c, nil
+}
+
+func commenterGetBySession(session string) (commenter, error) {
+	if session == "" {
+		return commenter{}, errorMissingField
+	}
+
+	statement := `
+    SELECT commenterHex
+    FROM commenterSessions
+    WHERE session=$1;
+	`
+	row := db.QueryRow(statement, session)
+
+	var commenterHex string
+	if err := row.Scan(&commenterHex); err != nil {
+		// TODO: is the only error?
+		return commenter{}, errorNoSuchSession
+	}
+
+	return commenterGetByHex(commenterHex)
+}