feat: added mail sender as env

[andrebrito16]

Hello, I noted that when running on self hosted there is no way to change the sender email. This is a problem, cause resend will not allow the email from openpanel domain.

This is a simple fix, should added on docs soon.

[CLAassistant]

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[lindesvard]

Thanks a lot and this is great but two thing:

• This env should be set here as well https://github.com/Openpanel-dev/openpanel/blob/main/self-hosting/.env.template (based on the domain you put into the wizard probably, or a new step to ask for resend api key and what domain should be used)
• Seems you need to install biome to get proper formatting

[andrebrito16]

I ran a biome format, and this should be ok now. About the installation, can you tell-me the file where I should modify. What I have in mind is:

1. Set domain
2. A step asks for sender with default "openpanel@domain"
3. Add to env

[lindesvard]

Sorry for late reply! Have been ignoring github the last couple of weeks to focus on infra.

I ran a biome format, and this should be ok now. About the installation, can you tell-me the file where I should modify. What I have in mind is:

1. Set domain
2. A step asks for sender with default "openpanel@domain"
3. Add to env

Add a new part here in this file https://github.com/Openpanel-dev/openpanel/blob/main/self-hosting/quiz.ts

I think this could be the final step. The question could be something like We use resend to send out emails (optional). Do you want to provide your api key?

Then we ask for the api key and from what email it should be sent as. The default email should be something like noreply@[the_domain_they_provided_in_the_first_step] (https://github.com/Openpanel-dev/openpanel/blob/main/self-hosting/quiz.ts#L178-L193)