[Backport 2.2-develop] Send email to subscribers only when are new

[osrecio]

Only send email/confirmation email of subscription to newsletter only when subscriber is new in newsletter

Description

Check if is necessary send email to a customer that is subscribed to newsletter. If this customer was subscribed previously not necessary send email.

Fixed Issues (if relevant)

1. Newsletter subscription #5439: Newsletter subscription

Manual testing scenarios

1. Subscribe an email not subscribed previously (e.g: test@test.com)
2. this email will receive a confirmation email of subscription
3. Subscribe the same email (test@test.com)
4. this email NOT will recieve a confirmation email of subscription

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[okorshenko]

Hi @osrecio
Could you please check dev/tests/integration/testsuite/Magento/Newsletter/Model/SubscriberTest.php : testEmailConfirmation

Magento\Newsletter\Model\SubscriberTest::testEmailConfirmation
Error: Call to a member function getBodyHtml() on null

/dev/tests/integration/testsuite/Magento/Newsletter/Model/SubscriberTest.php:36

You can execute it locally or wait for Travis results

[okorshenko]

Also, please check code style

Magento\Test\Php\LiveCodeTest::testCodeStyle
PHP Code Sniffer detected 2 violation(s): 

FILE: ./app/code/Magento/Newsletter/Model/Subscriber.php
----------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
----------------------------------------------------------------------
 449 | ERROR | [x] Expected 1 space after IF keyword; 0 found
(9 more lines...)

Same issues here: #11316

[okorshenko]

Hi @osrecio thank you for fixing code style. But more critical issue is in integration test: dev/tests/integration/testsuite/Magento/Newsletter/Model/SubscriberTest.php:testEmailConfirmation

[osrecio]

Yes, I know. Working on it. Thanks

[osrecio]

All tests passed :)