Configurable email senders

[Taeir]

Previously, all email senders were hardcoded in the source to be @codidact.com/@codidact.org email addresses. This changes those to be configurable.

• Creates configuration for all the emails QPixel can send
• Require both developer and global admin to send email to all users, rather than just developer.
• Avoid accidental send all users email by adding more warnings and confirmation
• Move buttons for email sending together in admin tools.
• Change setting category from EmailSubscriptions to just Email.

[ArtOfCode-]

LGTM - will wait for ready-to-merge status :)

[Taeir]

@cellio I added you as reviewer not for the code, but because I think it would be good for you to review whether the default email addresses configured actually make sense. Note also that these are modifiable per community.

For reference, here are the settings:

[cellio]

@Taeir I think SupportReceiverEmail should probably be [email protected] rather than info, but @ArtOfCode- please confirm.

Another question for Art: do we need a separate support address for donations, or can everything involving donations come down to DonationSenderName and DonationSenderEmail?

[ArtOfCode-]

Email addresses can basically be whatever we like - support should be support@, yes, and donations are fine to all come from one address