Added sample cds rule

.eslint/rules/no-open-services.js

@@ -0,0 +1,38 @@
+module.exports = {
+    meta: {
+      docs: {
+        description: "Service without `@requires/restrict` should not expose fields `createdBy` and `modifiedBy`.",
+        version: "1.0.0"
+      },
+      fixable: "code",
+      model: "inferred"
+    },
+    create: function (context) {
+      return { entity: checkForExposedFields };
+
+      function checkForExposedFields(e) {
+        const services = context.getModel().services;
+        const unauthorizedServices = services
+          .map((s) => {
+            if (!s["@requires"] && !s["@restrict"]) {
+              return s.name;
+            }
+          })
+          .filter((item) => !!item);
+        const found = Object.keys(e.elements).find((r) => ["createdBy", "modifiedBy"].indexOf(r) >= 0);
+        const isUnauthorizedService = unauthorizedServices.some((r) => {
+          if (e.name.includes(r)) {
+            return true;
+          }
+          return false;
+        });
+        if (found && isUnauthorizedService) {
+          context.report({
+            message: `Danger - exposed field '${found}' with '${e.name}' Either remove these or add add \`@restrict/requires\`.`,
+            node: context.getNode(e),
+            file: e.$location.file
+          });
+        }
+      }
+    }
+  };