fix(email): include course name in student welcome subject (#739)

* fix(email): include course name in student welcome subject

The studentCourseWelcome template used a static subject, so bulk course
assignments produced identical inbox titles. Resolve the subject from
courseName at send time and sanitize it like other email headers.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(email): use course-only subject for student welcome email

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

packages/email/src/core/base.ts

@@ -3,6 +3,7 @@ import * as z from 'zod';
 import type { EmailResponse } from '../utils/types';
 import type { SendTemplateConfig } from './types';
 import { deliverEmail } from '../send';
+import { sanitizeEmailSubject } from '../utils/functions/email-helpers';
 
 /**
  * Send a single email using a template
@@ -13,10 +14,14 @@ export async function sendTemplateEmail<TSchema extends z.ZodType>(
 ): Promise<EmailResponse[]> {
   const content = config.template.render(config.fields);
 
+  const resolvedSubject =
+    config.subject ??
+    (typeof config.template.subject === 'function' ? config.template.subject(config.fields) : config.template.subject);
+
   return deliverEmail([
     {
       to: config.to,
-      subject: config.subject ?? config.template.subject,
+      subject: sanitizeEmailSubject(resolvedSubject),
       content,
       from: config.from ?? config.template.from,
       replyTo: config.replyTo ?? config.template.replyTo,

packages/email/src/core/types.ts

@@ -6,7 +6,7 @@ import type { EmailId } from '../utils/types';
  * Base email template interface
  */
 export interface EmailTemplate<TSchema extends z.ZodType = z.ZodType> {
-  subject: string;
+  subject: string | ((fields: z.infer<TSchema>) => string);
   schema: TSchema;
   render: (fields: z.infer<TSchema>) => string;
   from?: string;
@@ -47,7 +47,7 @@ export interface SendTemplateConfig<TSchema extends z.ZodType = z.ZodType> exten
  */
 export interface DefineEmailConfig<TSchema extends z.ZodType = z.ZodType> {
   id: EmailId;
-  subject: string;
+  subject: string | ((fields: z.infer<TSchema>) => string);
   schema: TSchema;
   render: (fields: z.infer<TSchema>) => string;
   from?: string;

packages/email/src/emails/student-course-welcome.ts

@@ -6,7 +6,7 @@ import { ZEmailBranding } from '../core/branding';
 
 export const studentCourseWelcomeEmail = defineEmail({
   id: 'studentCourseWelcome',
-  subject: 'You have access to a course — sign in to get started',
+  subject: (fields) => `You have access to ${fields.courseName} course`,
   schema: z.object({
     orgName: z.string().min(1),
     courseName: z.string().min(1),