feat: Allow plaintext e-mails for SMTP

[jficz]

Adds --plaintext flag which allows sending
e-mails in plaintext with SMTP method.

Not implemented for the Resend method.

Fixes (partially?) #115

[jficz]

@aymanbagabas @andreynering @raphamorim
politely requesting a review :) Sorry for the ping, not sure what's your review process

[aymanbagabas]

Hi @jficz, this looks good!

Could you add POP_SMTP_PLAINTEXT=bool so that this option can be controlled by environment variables?

[raphamorim]

lgmt

[jficz]

Could you add POP_SMTP_PLAINTEXT=bool

sure, gimme a day or two

[jficz]

@aymanbagabas added as POP_PLAINTEXTas, strictly speaking, it doesn't have anything to do with SMTP (as in the protocol)

[jficz]

also, any chance of a release with this feat ?

[aymanbagabas]

@aymanbagabas added as POP_PLAINTEXTas, strictly speaking, it doesn't have anything to do with SMTP (as in the protocol)

Perfect!

Could you add Resend support as well? With Resend, we can omit the HTML version of the message when using plaintext

[jficz]

The reason I did not implement this for Resend is that, tbh, I did not really understand the code. I can take look but that will take more time.

[jficz]

@aymanbagabas tried in e1e08d4 but I have absolutely no idea if this will work 🤷‍♂️

I don't really understand the unsafe condition or how resend.SendEmailRequest works. Assuming it just ignores Html if the string is empty.