feat(admin-email): Add "Email Heading" as a customizable setting for all Emails

[mathetos]

User Story

As a Give Admin, I want to be able to fully customize my email content so that each email has a header that properly describes each form/campaign.

Current Behavior

I currently can customize the content of each email just fine; but I have to use a snippet in order to customize the email heading.

Expected Behavior

I expect to be able to customize the email heading as easily as I can customize the email content.

Possible Solution

Add the setting to the global email settings like so:

And the individual form edit screens like so:

Related

• Most recent user request (though they don't ask for it directly, it would help them a ton) https://wordpress.org/support/topic/display-language-view-not-correct/

Tasks

• Add the setting to the global email settings for each individual email
• Add the setting to the form edit screen for each individual email
• Ensure that email tags work in those settings so users can use {donor_name}, etc. in the email heading.
• Ensure that there are default values for the email heading in case the setting is not customized.

[kevinwhoffman]

@Sidsector9 To clarify, this is the text we are looking to customize at the top of each email.

Note that this field should be customizable in all emails from the Settings > Emails tab.

[ravinderk]

@mathetos @Sidsector9 We can create this as the default setting in Email API because most of our email notification support heading.