Improve now alias UX in case of an external DNS and a CNAME entry

lib/alias.js

@@ -150,9 +150,19 @@ module.exports = class Alias extends Now {
         if (domainInfo.verified) {
           skipDNSVerification = true
         } else if (domainInfo.uid) {
-          const e = new Error(`> The domain ${domain} is already registered with now but additional verification is needed, please refer to 'now domain --help'.`)
-          e.userError = true
-          throw e
+          const {verified, verifyToken, created} = await this.setupDomain(domain, {isExternal: true})
+
+          if (created && verified) {
+            console.log(`${chalk.cyan('> Success!')} Domain ${chalk.bold(chalk.underline(domain))} verified`)
+          } else if (verifyToken) {
+            const e = new Error(`> Verification required: Please add the following TXT record on the external DNS server: _now.${domain}: ${verifyToken}`)
+            e.userError = true
+            throw e
+          } else {
+            const e = new Error(`> Failed to verify the ownership of ${domain}, please refer to 'now domain --help'.`)
+            e.userError = true
+            throw e
+          }
         }
       }