Email stays associated with deleted user account

[TanyaStere42]

Context
Because of connections between user accounts, we need to maintain user's data access when an account is deleted. However, we should not maintain the email account in the database.

Expected Behavior
Inactive users are maintained for data connection history, but are no longer locked to a specific email account

Current Behavior
Creating a user with the same email address as a deleted user autopopulates their username with "inactivated user"

Example: Created an account in QA server and set up profile. Logged into admin account and deleted the new user. When I created a new account with the deleted email address, I wasn't prompted to set a name and accept the user agreement. I was taken to my profile page where it showed my name as Inactivated User.

I uploaded a sighting and deleted the user. The sighting remains in the system.

Following the link to the inactivated user's page from the sighting leads here:

Restoring the account also restores the previously submitted sightings. I manually updated the account name to test if it would link back to the original uploader.

QA Verification

1. Create user with test email
2. Create sighting for that user
3. Delete user
4. Verify sighting is now assigned to inactive user
5. create new user with test email
6. fresh new user created; no sightings, has to verify email, has to accept data agreement