feat(k8s): better form validation for configuration keys (#4728) (#4733)

Co-authored-by: Simon Meng <simon.meng@portainer.io>

app/kubernetes/helpers/formValidationHelper.js

@@ -1,6 +1,17 @@
 import _ from 'lodash-es';
 
 class KubernetesFormValidationHelper {
+  static getInvalidKeys(names) {
+    const res = {};
+    _.forEach(names, (name, index) => {
+      const valid = /^[-._a-zA-Z0-9]+$/.test(name);
+      if (!valid) {
+        res[index] = true;
+      }
+    });
+    return res;
+  }
+
   static getDuplicates(names) {
     const groupped = _.groupBy(names);
     const res = {};