Review messaging that describes when a FOSSA Account already exists at that email address

FOSSA will not send email invitations to join CNCF FOSSA to an email addresses that is already associated with an exising FOSSA account.

The maintainer then needs to be offered the choice of either

1. Abandoning their (typically personal and free) existing FOSSA account and then creating a new CNCF FOSSA account with that email address.

2. If they need to retain their existing account then the maintainer will need to associate a new email address with their Github account so that we can create new FOSSA account with that different email address.

Across the last three years I have had only one maintainer say, "I need that a/c for work"

Potentially we could automate sending of the support request to FOSSA Support.