MTV asks for a single certificate for RHV - if that certificates works for both getting the inventory data and getting the disks, everything works

However, users can configure different certificates for httpd and engine CA - in that case, MTV would be able to get the inventory data but would fail to execute the migration. We are missing a check that the entire process would work with the certificate that is specified for the provider (either a single certificate that works for both httpd and engine CA, or two certificates that are appended in that field). If this check fails, we should try to retrieve the engine CA certificate on the backend

As a first step, automatic retrieval of the engine CA certificate will happen in the backend in case the disk transfer fails due to it being missing and will be added to the existing one, no user interference will be needed.

As a next step, we can add some validation to this case and if both certs are required add an explicit message to let the users know, also add a new variable (and a new UI field) so they can provide both of the certificates while adding a new provider to the inventory.