Improve error reporting

[asifkazi]

DevGateway dies with internal server error if the workspace in the workload-dev-mode.json does not have a capacity assigned to it.

Developers are left clueless into what is going on can we provide better error reporting by doing pre-flight checks:

1. Is the workspace id correct or invalid
2. Is a capacity assigned to the workspace

Otherwise its trial and error to figure out what is going on

[SanchanaMohankumar]

Hi @asifkazi,
I encountered the same internal server error while running DevGateway, but after undoing each change, I identified that the problem originated from modifications made in item1.json and Product.json files. These changes did not pass the validation script located in the validation folder which resulted in DevGateway failure. Adding this point for future reference.
Thank you