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/smtp_configure.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"net/smtp"
+	"os"
+)
+
+var smtpConfigured bool
+var smtpAuth smtp.Auth
+
+func smtpConfigure() error {
+	username := os.Getenv("SMTP_USERNAME")
+	password := os.Getenv("SMTP_PASSWORD")
+	host := os.Getenv("SMTP_HOST")
+	if username == "" || password == "" || host == "" {
+		logger.Warningf("smtp not configured, no emails will be sent")
+		smtpConfigured = false
+		return nil
+	}
+
+	if os.Getenv("SMTP_FROM_ADDRESS") == "" {
+		logger.Errorf("SMTP_FROM_ADDRESS not set")
+		smtpConfigured = false
+		return errorMissingSmtpAddress
+	}
+
+	logger.Infof("configuring smtp: %s", host)
+	smtpAuth = smtp.PlainAuth("", username, password, host)
+	smtpConfigured = true
+	return nil
+}