Introduce Support for Mailerlite Embedded Forms

[donalirl]

The Problem
We introduced a Mailerlite (https://www.mailerlite.com/) popup integration in Automattic/jetpack#15878 that became part of the WordPress.com Editing Toolkit plugin. It's becoming a popular option, but for users who wish to use Mailerlite to manage their email list, a popup is the only integration we offer. Many site owners do not like popups, and wish to use a static embedded form instead.

The Potential Solution
I'd like to see us support a Mailerlite form integration, via a block or whitelisting the embed code. Mailerlite provides Javascript and HTML options, which are not supported on WordPress.com sites.

As a side note, Mailerlite have a plugin that includes both a widget and block: https://wordpress.org/plugins/official-mailerlite-sign-up-forms/

Alternatives
Mailerlite provides a third option: a URL for the form. This can be added to the site but it is not an embed. It takes visitors off of the user's site to Mailerlite's site to subscribe. Embeds directly on the site are more attractive to site owners.

Additional context
#user-report #25414796-hc

See Automattic/jetpack#17721 for additional discussion on the development of this feature.

[andrewserong]

@simison I think the Mailerlite integration might have been a hack week or side project, introduced in the Editing Toolkit plugin so I believe it's currently unowned. (It gets registered here: https://github.com/automattic/wp-calypso/blob/trunk/apps%2Fediting-toolkit%2Fediting-toolkit-plugin%2Ffull-site-editing-plugin.php#L310).

I think this is a great idea for an enhancement, though. Is this a good one for our prioritised backlog, or do you think it better belongs with View or Manage?

[simison]

@andrewserong Yeah, this is better handled by other teams.

[jordesign]

Another user requesting this in #3825489-zen

it looks like the original work was done by @artpi - who might have some further thoughts on adding a block or oEmbed.
this seems it would be a great thing to add to further our MailerLite integration.

[artpi]

who might have some further thoughts on adding a block or oEmbed.

I think we should do it :) Here is how: Automattic/jetpack#17721 (comment)

[jamiepalatnik]

Another request for MailerLite integration: 4962472-zd-woothemes

MailerLite has released a new version of the Mailerlite and the JavaScript tracking snippet doesn't have any UUID.

In the Mailerlite widget, there is an option to add an account ID and UUID but the new MailerLite tracking snippet doesn't have any UUID. So it seems that users that have transitioned to the new Mailerlite currently cannot use the popup widget either.

Context: 1521-gh-Automattic/en.support-docs-content