tmc delete requires -m and -p options

[ccollicutt]

In order to detach a tmc cluster that was attached, you have to use delete, but also the -m and -p options are required though the CLI doesn't specify that. Without those options you get an error message such as the below:

x rpc error: code = InvalidArgument desc = invalid DeleteClusterRequest.FullName: embedded message failed validation | caused by: invalid FullName.ProvisionerName: value must be a valid Tanzu name | caused by: a name cannot be empty or be longer than 63 characters 

eg. correct command:

tmc cluster delete $CLUSTER_NAME --force -m attached -p attached

"attached" is what tmc cluster list will show for both MANAGEMENTCLUSTER and PROVISIONER.