feat: Allow disabling email notifications for groups about gatus

[tarocjsu]

Just not set alert the email type for each endpoints.

[ffflorian]

@tarocjsu Sorry, I didn't get that... What do you mean?

[salim-b]

I guess what they meant is that as a workaround, you could set alerting.email.default-alert.enabled: false and then enable e-mail alerts on all the endpoints of the production group.

[ffflorian]

@salim-b oh, good idea. Thanks! But it's still a workaround..

[TwiN]

As was suggested, you should just manually enable them in each independent endpoint configuration instead of using alerting.email.default-alert.enabled: true.