Update error message when variables for secret provider is missing

Proposal

We check to see if variables are present to determine if a provider is available. If any of these are incorrect or missing, we display The secrets provider can not be found but don't indicate clearly what causes this or why it is not found. We should edit this message to be more clear like The secrets provider can not be found. Please check your CI/CD variables and try again.

Since this applies to 3 different providers, having a clearer error message is probably a better option than 3 troubleshooting sections in our documents.

Came up in ZD Ticket