When inviting a manager as a client and using an email address that matches no existing clients a success message is shown:

"An invitation was successfully sent to the matching user on record."

The invite shows up in account_management_invitations with a status of "invalid", but NOTHING is shown for "Invited Managers". The invitation is simply gone. No email is sent to the invitee.

If someone registers a client account with the email address, then the invite will now appear, but it appears as "Pending". It can then be revoked.

If it is not revoked, a client can sign up with this email and accept the invitation, assuming they can obtain the token. I don't recall if an invite can be accepted from the client account with no email.

In the future, we may want to be able to invite people who do not yet have an account. That invitation may invite them to create an account. For now, if there is no client account matching the email then we should:

1. Show an error message instead "An invitation could not be sent. Make sure the email address is correct or ask the user to register first."
2. Do not add the invitation to account_management_invitations