Add SMTP_HELLO_NAME to let operators set the EHLO/HELO identity

Google Workspace SMTP relay (smtp-relay.gmail.com) rejects generic
EHLO identifiers such as "localhost", which is Go net/smtp's default.
Operators can now set SMTP_HELLO_NAME to a valid hostname so that
c.Hello() is called before StartTLS, satisfying strict relay policies.

Fixes https://github.com/getprobo/probo/issues/1284

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/bootstrap/builder.go

@@ -166,6 +166,7 @@ func (b *Builder) Build() (*probodconfig.FullConfig, error) {
 						User:        b.getEnv("SMTP_USER"),
 						Password:    b.getEnv("SMTP_PASSWORD"),
 						TLSRequired: b.getEnvBoolOrDefault("SMTP_TLS_REQUIRED", false),
+						HelloName:   b.getEnv("SMTP_HELLO_NAME"),
 					},
 				},
 				Slack: probodconfig.SlackConfig{

pkg/bootstrap/builder_test.go

@@ -192,6 +192,7 @@ func TestBuilder_Build_Defaults(t *testing.T) {
 	assert.Equal(t, "no-reply@notification.getprobo.com", cfg.Probod.Notifications.Mailer.SenderEmail)
 	assert.Equal(t, "localhost:1025", cfg.Probod.Notifications.Mailer.SMTP.Addr)
 	assert.False(t, cfg.Probod.Notifications.Mailer.SMTP.TLSRequired)
+	assert.Empty(t, cfg.Probod.Notifications.Mailer.SMTP.HelloName)
 	assert.Equal(t, 60, cfg.Probod.Notifications.Mailer.MailerInterval)
 	assert.Equal(t, 60, cfg.Probod.Notifications.Slack.SenderInterval)
 	assert.Empty(t, cfg.Probod.Notifications.Slack.SigningSecret)