Added Mailchimp Email Adapater

[AVDiv]

What does this PR do?

This PR contains an implementation of the mailchimp transactional email adapter.

Test Plan

1. Setup your mailchimp account

• First of all, Create a Mailchimp account and set it up.

2. Setup the Mandrill credentials

• When you reach the dashboard, find for the option Automations > Transactional Emails on the left navigation pane.
• In this page you will find a Launch App
• Once you reach the mandrill dashboard, you will need to verify your Sending Domains . For that you have to go to Domains > Sending Domains. Next Add your domain, verify your Domain and DKIM settings by adding the relevant TXT records on your DNS.
• Once you are done with that, you can proceed to creating a new API key on SMTP & API Info > New API Key. Also don't forget to copy the API Key to somewhere safe.

3. Install relevant PHP Extensions and Dependencies

• You require PHP-extensions like php-curl to run this project, so make sure to get them installed first.

Example (linux-based systems):

sudo apt update &&
sudo apt install php-curl php-mbstring php-xml

• Next, install the relevant project dependecies by using composer

composer install

3. Test the project with relevant Environment Variables

TEST_EMAIL - The recipient email address
TEST_EMAIL_FROM - The sender email address
MAILCHIMP_API_KEY - The mailchimp API key

• Fill there 3 environment variables and run the following command to test:

MAILCHIMP_API_KEY=<YOUR_MAILCHIMP_API_KEY> TEST_EMAIL=<YOUR_RECIPIENT_EMAIL> TEST_FROM_EMAIL=<YOUR_SENDER_EMAIL> ./vendor/bin/phpunit tests/e2e/Email/MailchimpTest.php

Related PRs and Issues

closes: appwrite/appwrite#6388

Have you read the Contributing Guidelines on issues?

Yes

[wess]

Please run pint/linter :)

[AVDiv]

@wess Resolved linting errors, Please check now.
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[AVDiv]

Hey @wess, any updates?

[stnguyen90]

Looks good! Please also attach a screenshot of successful test

[AVDiv]

These are the test results

[stnguyen90]

Hey 👋 awesome work on your PR! We've approved your work and it'll be merged soon!