Don't require plugins to have executables

Since the Terraform plugin can consume credentials of other plugins, there is now a use-case for plugins with no executables.
If a service offers a Terraform provider, but no CLI, Shell Plugins should still offer a solution to allow for the provisioning of that credential.

Author: hculea

cmd/contrib/main.go

@@ -100,9 +100,8 @@ func newPlugin() error {
 			Validate: survey.Required,
 		},
 		{
-			Name:     "Executable",
-			Prompt:   &survey.Input{Message: `Executable name (e.g. "aws" or "gh") [required]`},
-			Validate: survey.Required,
+			Name:   "Executable",
+			Prompt: &survey.Input{Message: `Executable name (e.g. "aws" or "gh")`},
 		},
 		{
 			Name: "CredentialName",