fix: add multi email transport system (#2942)

packages/email/transports/build-transport.ts

@@ -0,0 +1,51 @@
+import type { TEmailTransportConfig } from '@documenso/lib/server-only/email/email-transport-config';
+import { ResendTransport } from '@documenso/nodemailer-resend';
+import type { Transporter } from 'nodemailer';
+import { createTransport } from 'nodemailer';
+
+import { MailChannelsTransport } from './mailchannels';
+
+export const buildTransport = (config: TEmailTransportConfig): Transporter => {
+  switch (config.type) {
+    case 'MAILCHANNELS':
+      return createTransport(
+        MailChannelsTransport.makeTransport({
+          apiKey: config.apiKey,
+          endpoint: config.endpoint,
+        }),
+      );
+
+    case 'RESEND':
+      return createTransport(
+        ResendTransport.makeTransport({
+          apiKey: config.apiKey,
+        }),
+      );
+
+    case 'SMTP_API':
+      return createTransport({
+        host: config.host,
+        port: config.port,
+        secure: config.secure,
+        auth: {
+          user: config.apiKeyUser ?? 'apikey',
+          pass: config.apiKey,
+        },
+      });
+
+    case 'SMTP_AUTH':
+      return createTransport({
+        host: config.host,
+        port: config.port,
+        secure: config.secure,
+        ignoreTLS: config.ignoreTLS,
+        auth: config.username
+          ? {
+              user: config.username,
+              pass: config.password ?? '',
+            }
+          : undefined,
+        ...(config.service ? { service: config.service } : {}),
+      });
+  }
+};