docs: revamped endpoints, services, and entities (#4660)

* revamp create endpoint docs

* docs: revamped endpoints, services, and entities

* eslint fixes

* fix metadata

* fix missing closing tag

* fixes to create migration doc

* fixes to create endpoint doc

* small fix in create service doc

www/docs/sidebars.js

@@ -1248,6 +1248,11 @@ module.exports = {
               id: "development/entities/create",
               label: "Create an Entity",
             },
+            {
+              type: "doc",
+              id: "development/entities/repositories",
+              label: "Use a Repository",
+            },
             {
               type: "doc",
               id: "development/entities/extend-entity",