Feature: add failed donation email

[glaubersilva]

Resolves GIVE-2646

Description

This PR adds a new email that is sent to the admin when a donation gets the status changes do failed.

Affects

Admin email notifications

Visuals

Testing Instructions

1. Create a test donation
2. Set the donation status to Failed
3. Make sure the new email was sent to the admin

Pre-review Checklist

• Acceptance criteria satisfied and marked in related issue
• Relevant @unreleased tags included in DocBlocks
• Includes unit tests
• Reviewed by the designer (if follows a design)
• Self Review of code and UX completed

[jonwaldstein]

@glaubersilva FYI I think there's 2 parts to this task that we'll need to decipher from the feedback.

1. Admin email: A donation status changes to failed (this PR)
2. Admin email: A subscription is marked as failing (a separate PR)

A version of #2 technically exists for the donor side but people also want to be notified as the admin.

[jonwaldstein]

Looks good, ready for QA 🌈

[glaubersilva]

@jonwaldstein I agree we need to create a new email for subscription failing to be sent for the admin, but I'll create a new task for that for better tracking and QA purposes.

[Robincredible]

QA Passed