Merge ghost users with same email in different case

[athyuttamre]

We have many ghost accounts (created either via the "Add TA" form, or via the multiple-student tickets form) with the same email IDs, but in different cases e.g. 'john_doe@brown.edu', and 'John_Doe@brown.edu'.

To fix this issue, we need to do the following:

• Lowercase, trim, and validate emails before creating accounts via these two places
• Write a migration that does the following:
  • Create a map of all sanitized emails with multiple user IDs associated with them

    { 'john_doe@brown.edu': [userId1, userId2, etc.]
    

  • For each such group, pick one user ID as the canonical one. Update the document to have the sanitized email.
  • Iterate through queues, and update all user ID fields to map from the other users to the picked user
  • Iterate through tickets, and update all user ID fields like above (including fields like userIds, createdBy etc.)