Save subscriptions when saving newsletters (#447)

* parse unsub mailTo or httpUrl and send to pubsub

* save subscription from newsletter

* fix tests

packages/inbound-email-handler/src/substack-handler.ts

@@ -7,15 +7,19 @@ export class SubstackHandler extends NewsletterHandler {
     this.defaultUrl = 'https://www.substack.com'
   }
 
-  getNewsletterUrl(rawUrl: string, _html: string): string | undefined {
+  getNewsletterUrl(postHeader: string, _html: string): string | undefined {
     // raw SubStack newsletter url is like <https://hongbo130.substack.com/p/tldr>
     // we need to get the real url from the raw url
-    return addressparser(rawUrl).length > 0
-      ? addressparser(rawUrl)[0].name
+    return addressparser(postHeader).length > 0
+      ? addressparser(postHeader)[0].name
       : undefined
   }
 
-  isNewsletter(rawUrl: string, _from: string, _unSubRawUrl: string): boolean {
-    return !!rawUrl
+  isNewsletter(
+    postHeader: string,
+    _from: string,
+    _unSubHeader: string
+  ): boolean {
+    return !!postHeader
   }
 }