Add beforeSend hook for email customization

- Add BeforeSendHook type and BeforeSendMailOptions interface
- Implement hook execution in MailingService before sending emails
- Hook allows adding attachments, headers, and modifying email options
- Add comprehensive documentation with examples
- Bump version to 0.1.20

src/sendEmail.ts

@@ -83,25 +83,25 @@ export const sendEmail = async <TEmail extends BaseEmailDocument = BaseEmailDocu
   if (emailData.to) {
     emailData.to = parseAndValidateEmails(emailData.to as string | string[])
   }
-  if (emailData.cc && emailData.cc !== null) {
+  if (emailData.cc) {
     emailData.cc = parseAndValidateEmails(emailData.cc as string | string[])
   }
-  if (emailData.bcc && emailData.bcc !== null) {
+  if (emailData.bcc) {
     emailData.bcc = parseAndValidateEmails(emailData.bcc as string | string[])
   }
-  if (emailData.replyTo && emailData.replyTo !== null) {
+  if (emailData.replyTo) {
     const validated = parseAndValidateEmails(emailData.replyTo as string | string[])
     // replyTo should be a single email, so take the first one if array
     emailData.replyTo = validated && validated.length > 0 ? validated[0] : undefined
   }
-  if (emailData.from && emailData.from !== null) {
+  if (emailData.from) {
     const validated = parseAndValidateEmails(emailData.from as string | string[])
     // from should be a single email, so take the first one if array
     emailData.from = validated && validated.length > 0 ? validated[0] : undefined
   }
 
   // Sanitize fromName to prevent header injection
-  if (emailData.fromName && emailData.fromName !== null) {
+  if (emailData.fromName) {
     emailData.fromName = emailData.fromName
       .trim()
       // Remove/replace newlines and carriage returns to prevent header injection