validate shortnames during generation

[mitchdraft]

"nice to have"

currently you can generate code with kube shortcodes like this: shortCode but if you try to register the crd, it will fail with this error:

0: errorVerbose: failed to register crd: CustomResourceDefinition.apiextensions.k8s.io "rbacconfigs.istio.rbac.v1alpha1" is invalid: spec.names.shortNames[0]: Invalid value: "rbacConfig": a DNS-1035 label must consist of lower case alphanumeric characters or '-', start with an alphabetic character, and end with an alphanumeric character (e.g. 'my-name',  or 'abc-123', regex used for validation is '[a-z]([-a-z0-9]*[a-z0-9])?')
creating base RbacConfig resource client
github.com/solo-io/mesh-projects/vendor/github.com/solo-io/solo-kit/pkg/errors.Wrapf
        /Users/mitch/go/src/github.com/solo-io/mesh-projects/vendor/github.com/solo-io/solo-kit/pkg/errors/errors.go:12
github.com/solo-io/mesh-projects/pkg/api/external/istio/rbac/v1alpha1.NewRbacConfigClientWithToken
        /Users/mitch/go/src/github.com/solo-io/mesh-projects/pkg/api/external/istio/rbac/v1alpha1/rbac_config_client.sk.go:41
github.com/solo-io/mesh-projects/pkg/api/external/istio/rbac/v1alpha1.NewRbacConfigClient
        /Users/mitch/go/src/github.com/solo-io/mesh-projects/pkg/api/external/istio/rbac/v1alpha1/rbac_config_client.sk.go:32
github.com/solo-io/mesh-projects/pkg/capability/rbac.InitializeRbacConfigClient
        /Users/mitch/go/src/github.com/solo-io/mesh-projects/pkg/capability/rbac/rbac_syncer.go:256
github.com/solo-io/mesh-projects/pkg/capability/rbac.Run
        /Users/mitch/go/src/github.com/solo-io/mesh-projects/pkg/capability/rbac/rbac_syncer.go:52
github.com/solo-io/mesh-projects/services/rbac-operator/pkg/setup.Main
        /Users/mitch/go/src/github.com/solo-io/mesh-projects/services/rbac-operator/pkg/setup/setup.go:33
main.run.func1
        /Users/mitch/go/src/github.com/solo-io/mesh-projects/services/rbac-operator/cmd/main.go:26
runtime.goexit
        /usr/local/Cellar/go/1.12.5/libexec/src/runtime/asm_amd64.s:1337
process: rbac-operator
logger: rbac-operator
msg: err in main
caller: cmd/main.go:17
version: undefined
error: creating base RbacConfig resource client: failed to register crd: CustomResourceDefinition.apiextensions.k8s.io "rbacconfigs.istio.rbac.v1alpha1" is invalid: spec.names.shortNames[0]: Invalid value: "rbacConfig": a DNS-1035 label must consist of lower case alphanumeric characters or '-', start with an alphabetic character, and end with an alphanumeric character (e.g. 'my-name',  or 'abc-123', regex used for validation is '[a-z]([-a-z0-9]*[a-z0-9])?')
stacktrace: main.main
        /Users/mitch/go/src/github.com/solo-io/mesh-projects/services/rbac-operator/cmd/main.go:17
runtime.main
        /usr/local/Cellar/go/1.12.5/libexec/src/runtime/proc.go:200
level: fatal
ts: 2019-11-06T10:41:28.299-0500

it's tricky because plural_name does not have this restriction

example of valid config:

message RbacConfig {

    option (core.solo.io.resource).short_name = "rbacconfig";
    option (core.solo.io.resource).plural_name = "rbacConfigs";

example of invalid config:

message RbacConfig {

    option (core.solo.io.resource).short_name = "rbacConfig";
    option (core.solo.io.resource).plural_name = "rbacConfigs";

if we validate during generation we can signal this error sooner than later