[ENG-4903] Fixes issue with email confirmation links failing due to database congestion

[uditijmehta]

Purpose

Move email confirmation to a post-commit task.

Changes

• Moved send_confirm_email call to a post-commit task in UserEmailsSerializer.
• Defined send_confirm_email_async to handle email sending after database transactions are committed.

QA Notes

The send_confirm_email function has been refactored to send_confirm_email_async across various parts of the codebase.

• API User Email Creation (api/users/serializers.py):
  Scenario: Adding a new email address to a user profile.

• API User Email Resend Confirmation (api/users/views.py):
  Scenario: Resending confirmation email.

• User Registration (framework/auth/views.py):
  Scenario: New user registration.

• Resend Confirmation Email (framework/auth/views.py):
  Scenario: Resending a confirmation email.

• External Login Email Handling (framework/auth/views.py):
  Scenario: Handling email submission for first-time OAuth login user.

• Resend Confirmation Email from Profile (website/profile/views.py):
  Scenario: Resending a confirmation email from user profile.

• Update User Profile Emails (website/profile/views.py):
  Scenario: Adding a new email to the user profile.

• General Email Throttling:
  Scenario: Ensuring email throttling is respected.

Ticket

https://openscience.atlassian.net/browse/ENG-4903

[cslzchen]

2nd pass done 🎆 I have a suggestion for QA notes and have a question on using local functions.

[cslzchen]

Update: changed base branch to feature/b-and-i-24-14

[cslzchen]

Looks great! Thanks for the quick response and great QA notes.