The %OAuth2.Server.JWT is the GenerateTokernClass which creates a JWT which is included with the server. The GenerateTokenClass is specified in the Authorization Server Configuration. It must contain a GenerateAccessToken method will be used to generate an access token based on the array of properties that is returned by the ValidateUser method.
Add requested claims to the JWT
The GenerateAccessToken method returns an optionally signed and/or encryypted JWT to be used as an access token. The access token may be based on the properties argument. In addition values for claims to be added to the JSON response object may be returned in the properties.ResponseProperties array.
However the method in this default class just returns a JWT which is optionally signed and/or encrypted.
The IsJWT method returns true if the GenerateAccessToken method returns a JWT. IsJWT is used to determine inclusion of algorithms for access token in server metadata.