🚀 BREAKING: Simplify API to use Payload collections directly

- Remove complex sendEmail/scheduleEmail methods and SendEmailOptions types
- Add simple renderTemplate() helper for template rendering
- Users now create emails using payload.create() with full type safety
- Leverage Payload's existing collection system instead of duplicating functionality
- Provide comprehensive migration guide and usage examples

BREAKING CHANGES:
- sendEmail() and scheduleEmail() methods removed
- SendEmailOptions type removed
- Use payload.create() with email collection instead
- Use renderTemplate() helper for template rendering

Benefits:
✅ Full TypeScript support with generated Payload types
✅ Use any custom fields in your email collection
✅ Leverage Payload's validation, hooks, and access control
✅ Simpler, more consistent API
✅ Less code to maintain

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

simplified-api-guide.md

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+# Simplified API Guide
+
+The mailing plugin now uses a much simpler, type-safe API that leverages PayloadCMS's existing collection system instead of custom email methods.
+
+## New API Approach
+
+### ✅ **Recommended: Use Payload Collections Directly**
+
+```typescript
+import { payload, renderTemplate } from '@xtr-dev/payload-mailing'
+
+// 1. Render a template (optional)
+const rendered = await renderTemplate(payload, 'welcome-email', {
+  name: 'John Doe',
+  activationLink: 'https://example.com/activate/123'
+})
+
+// 2. Create an email using Payload's collection API
+const email = await payload.create({
+  collection: 'emails', // Your email collection name
+  data: {
+    to: ['user@example.com'],
+    subject: rendered.subject, // or your own subject
+    html: rendered.html,       // or your own HTML
+    text: rendered.text,       // or your own text
+    // Add any custom fields you've defined in your collection
+    priority: 1,
+    scheduledAt: new Date('2024-01-01T10:00:00Z'), // Optional scheduling
+  }
+})
+```
+
+### ❌ **Old API (Removed)**
+
+```typescript
+// These methods have been removed to simplify the API
+await sendEmail(payload, { to: '...', subject: '...' })
+await scheduleEmail(payload, { to: '...', scheduledAt: new Date() })
+```
+
+## Benefits of the New Approach
+
+### 🎯 **Type Safety**
+- Full TypeScript support using your generated Payload types
+- IntelliSense for all your custom collection fields
+- Compile-time validation of email data
+
+### 🚀 **Flexibility**
+- Use any fields you've added to your email collection
+- Leverage Payload's built-in validation, hooks, and access control
+- Full control over email data structure
+
+### 🧹 **Simplicity**
+- One consistent API (Payload collections) instead of custom methods
+- No duplicate type definitions
+- Less code to maintain
+
+## Usage Examples
+
+### Basic Email with Template
+```typescript
+import { renderTemplate } from '@xtr-dev/payload-mailing'
+
+const { html, text, subject } = await renderTemplate(payload, 'order-confirmation', {
+  orderNumber: '#12345',
+  customerName: 'Jane Smith',
+  items: [
+    { name: 'Product 1', price: 29.99 },
+    { name: 'Product 2', price: 49.99 }
+  ]
+})
+
+await payload.create({
+  collection: 'emails',
+  data: {
+    to: ['customer@example.com'],
+    subject,
+    html,
+    text,
+    priority: 2,
+    // Add your custom fields
+    orderId: '12345',
+    customerSegment: 'premium'
+  }
+})
+```
+
+### Bulk Email Creation
+```typescript
+const customers = await payload.find({
+  collection: 'customers',
+  where: { newsletter: { equals: true } }
+})
+
+for (const customer of customers.docs) {
+  const { html, text, subject } = await renderTemplate(payload, 'newsletter', {
+    name: customer.name,
+    unsubscribeLink: `https://example.com/unsubscribe/${customer.id}`
+  })
+
+  await payload.create({
+    collection: 'emails',
+    data: {
+      to: [customer.email],
+      subject,
+      html,
+      text,
+      scheduledAt: new Date('2024-01-15T09:00:00Z'), // Send next week
+    }
+  })
+}
+```
+
+### Direct HTML Email (No Template)
+```typescript
+await payload.create({
+  collection: 'emails',
+  data: {
+    to: ['admin@example.com'],
+    subject: 'System Alert',
+    html: '<h1>Server Error</h1><p>Please check the logs immediately.</p>',
+    text: 'Server Error: Please check the logs immediately.',
+    priority: 10, // High priority
+  }
+})
+```
+
+## Available Helper Functions
+
+```typescript
+import {
+  renderTemplate,    // Render email templates with variables
+  processEmails,     // Process pending emails manually
+  retryFailedEmails, // Retry failed emails
+  getMailing        // Get mailing service instance
+} from '@xtr-dev/payload-mailing'
+```
+
+## Migration Guide
+
+If you were using the old `sendEmail`/`scheduleEmail` methods, update your code:
+
+**Before:**
+```typescript
+await sendEmail(payload, {
+  templateSlug: 'welcome',
+  to: 'user@example.com',
+  variables: { name: 'John' }
+})
+```
+
+**After:**
+```typescript
+const { html, text, subject } = await renderTemplate(payload, 'welcome', { name: 'John' })
+
+await payload.create({
+  collection: 'emails',
+  data: {
+    to: ['user@example.com'],
+    subject,
+    html,
+    text
+  }
+})
+```
+
+This new approach gives you the full power and type safety of PayloadCMS while keeping the mailing functionality simple and consistent! 🚀