feat: Move mail system to shared

shared/mail/account.go

@@ -0,0 +1,37 @@
+package mail
+
+import (
+	"fmt"
+	"time"
+)
+
+// VerifyWindow is how long a verification or invitation link stays usable. It
+// is stated in the email, so it lives beside the message rather than in the
+// caller.
+const VerifyWindow = 24 * time.Hour
+
+// SendVerification asks someone to confirm the address they signed up with.
+// The link is built from the Sender's PublicURL, because the address of the
+// portal is a property of the deployment, not of the call site.
+func (s Sender) SendVerification(to, token string) error {
+	return s.sendTemplate(to, "", "verification", struct {
+		Link     string
+		TTLHours int
+	}{
+		Link:     fmt.Sprintf("%s/verify?token=%s", s.PublicURL, token),
+		TTLHours: int(VerifyWindow.Hours()),
+	})
+}
+
+// SendInvite asks someone to join an existing account and set their own
+// password. It names the account, because an unexpected invitation from a
+// service you have never used is otherwise indistinguishable from spam.
+func (s Sender) SendInvite(to, accountName, token string) error {
+	return s.sendTemplate(to, "", "invite", struct {
+		AccountName string
+		Link        string
+	}{
+		AccountName: accountName,
+		Link:        fmt.Sprintf("%s/accept-invite?token=%s", s.PublicURL, token),
+	})
+}