Tailor signature certificate email copy for approvals

Store the per-signature email subject as text on the electronic_signatures
row at creation time, mirroring the consent_text pattern. The document
approval service sets "Your approved <Title> - Certificate of Completion";
other callers default to "Your signed <Name> - Certificate of Completion".
The certificate worker uses signature.email_subject as the email subject,
falling back to the default format when the column is empty.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/esign/completion_certificate_worker.go

@@ -271,7 +271,12 @@ func (h *completionCertificateHandler) generateCertificate(
 		docName = signature.DocumentType.DisplayName()
 	}
 
-	subject, textBody, htmlBody, err := emailPresenter.RenderElectronicSignatureCertificate(ctx, ref.UnrefOrZero(signature.SignerFullName), docName)
+	subject := signature.EmailSubject
+	if subject == "" {
+		subject = fmt.Sprintf("Your signed %s - Certificate of Completion", docName)
+	}
+
+	textBody, htmlBody, err := emailPresenter.RenderElectronicSignatureCertificate(ctx, ref.UnrefOrZero(signature.SignerFullName), docName, subject)
 	if err != nil {
 		return nil, nil, fmt.Errorf("cannot render email: %w", err)
 	}