feat: Support Regex validation for custom attributes (#7856)

This allows a user to add/update a custom regex and a cue while defining custom attributes(Only applicable for type- text).
While adding/editing custom attributes, the values are validated against the attribute definition regex, and if it is incorrect, a cue message or default error message is shown and restricts invalid values from being saved.

Fixes: #6866

app/javascript/dashboard/mixins/customAttributeMixin.js

@@ -0,0 +1,11 @@
+export default {
+  methods: {
+    getRegexp(regexPatternValue) {
+      let lastSlash = regexPatternValue.lastIndexOf('/');
+      return new RegExp(
+        regexPatternValue.slice(1, lastSlash),
+        regexPatternValue.slice(lastSlash + 1)
+      );
+    },
+  },
+};