Document how to send emails in LB4

[dhmlau]

Description / Steps to reproduce / Feature proposal

Originated from #1971

In LoopBack 3, users can use our email connector to send emails.
Ideally, we can use the same connector in LoopBack 4 the same way we use other connectors. However, the email connector is part of the LB3 core, so cannot be used as-is.

We've listed the workaround in this comment: #1971 (comment).

Acceptance Criteria

• Remove email connector option when running lb4 datasource command, since this won't work.
• Document the workaround in the LB4 documentation page

cc @bajtos

[manishbalodia]

Need docs or example to configure mail in loopback 4

[djamaile]

So has anyone a real example on how to send email in lb4?

[Riplar]

@djamaile just use nodemailer for now. I implemented it as a service:

import {SentMessageInfo} from 'nodemailer';
import Mail = require('nodemailer/lib/mailer');
import params from '../data/params'

const nodemailer = require("nodemailer");

export class MailerService {
  async sendMail(mailOptions: Mail.Options): Promise<SentMessageInfo> {
    const transporter = nodemailer.createTransport(params.mail_account);
    return await transporter.sendMail(mailOptions);
  }
}

And then you just have to inject the MailerService in your controller and use it like this:

let info = await this.mailerService.sendMail({
      to: foundUser.email,
      subject: "Testmail",
      html: '<p>This is a mail</p>'
    });

[sureshdmavericks]

@RipkensLar , Can you explain ../data/params?

[sureshdmavericks]

Thanks @RipkensLar . Its worked like a charm... Thank you

[syntheticgoo]

@RipkensLar , Can you explain ../data/params?

see: https://nodemailer.com/smtp/

[mrbatista]

@dhmlau Available to port LB3 Email connector to LB4.

[dhmlau]

@mrbatista, that would be great. Thanks.
In case you're not aware already, @bajtos and I had some discussion on this earlier, the notes are captured in #1971 (comment).

Let me assign this issue to you now. Thanks again.

[dougal83]

Down the road, it could be expanded with something like https://www.npmjs.com/package/email-templates for example. An API would most likely be firing out templated messages.