OAuth authentication error: user cannot be claimed by identity because it is already mapped

Issue

• Login to the platform with a certain valid user fails with:

Error from server (InternalError): Internal error occurred: unexpected response: 500

• After setting debug log level in authentication operator we can see:

"Error: user <user> cannot be claimed by identity <identity>:<user> because it is already mapped to <identity2>:<user>"

• Oauth login fails for a user when the same login account is available from two different identity providers.