Rework FromAddress to prevent all the nesting

fromaddress.go

@@ -5,17 +5,24 @@ import (
 	"github.com/emersion/go-message/mail"
 )
 
-type FromAddress struct {
-	*mail.Address
-}
+type FromAddress mail.Address
 
 var _ encoding.TextUnmarshaler = &FromAddress{}
 
+func (f FromAddress) String() string {
+	return f.toMailAddress().String()
+}
+
 func (f *FromAddress) UnmarshalText(b []byte) error {
 	address, err := mail.ParseAddress(string(b))
 	if err != nil {
 		return err
 	}
-	f.Address = address
+	*f = FromAddress(*address)
 	return nil
 }
+
+func (f FromAddress) toMailAddress() *mail.Address {
+	m := mail.Address(f)
+	return &m
+}

fromaddress_test.go

@@ -11,13 +11,13 @@ func TestFromAddress_UnmarshalText(t *testing.T) {
 	t.Run("json", func(t *testing.T) {
 		var fromAddress FromAddress
 		assert.NoError(t, json.Unmarshal([]byte(`"Jane Doe <jane@example.com>"`), &fromAddress))
-		assert.Equal(t, "Jane Doe", fromAddress.Address.Name)
-		assert.Equal(t, "jane@example.com", fromAddress.Address.Address)
+		assert.Equal(t, "Jane Doe", fromAddress.Name)
+		assert.Equal(t, "jane@example.com", fromAddress.Address)
 	})
 	t.Run("yaml", func(t *testing.T) {
 		var fromAddress FromAddress
 		assert.NoError(t, yaml.Unmarshal([]byte(`"Jane Doe <jane@example.com>"`), &fromAddress))
-		assert.Equal(t, "Jane Doe", fromAddress.Address.Name)
-		assert.Equal(t, "jane@example.com", fromAddress.Address.Address)
+		assert.Equal(t, "Jane Doe", fromAddress.Name)
+		assert.Equal(t, "jane@example.com", fromAddress.Address)
 	})
 }

mail.go

@@ -77,7 +77,7 @@ func (m *Mail) SendMail(subject string, to []*mail.Address, htmlBody, textBody i
 	var h mail.Header
 	h.SetDate(time.Now())
 	h.SetSubject(subject)
-	h.SetAddressList("From", []*mail.Address{m.From.Address})
+	h.SetAddressList("From", []*mail.Address{m.From.toMailAddress()})
 	h.SetAddressList("To", to)
 	h.Set("Content-Type", "multipart/alternative")