If an email address of an existing user is invited to the platform, there is no way to accept to join the new institution

[dave-mills]

Suggestion:

• Validate the Invite creation. If the entered email already exists, give the current user a message saying "this user already exists on the platform. Their role is ${role}. Do you want to add them to this project with that role?

• If you need to add them to a different role, you will need to use a different email address for them.