docs: updates to use DML and other changes (#7834)

- Change existing data model guides and add new ones for DML
- Change module's docs around service factory + remove guides that are now necessary
- Hide/remove all mentions of module relationships, or label them as coming soon.
- Change all data model creation snippets to use DML
- use `property` instead of `field` when referring to a data model's properties.
- Fix all snippets in commerce module guides to use new method suffix (no more main model methods)
- Rework recipes, removing/hiding a lot of sections as a lot of recipes are incomplete with the current state of DML.


### Other changes

- Highlight fixes in some guides
- Remove feature flags guide
- Fix code block styles when there are no line numbers.

### Upcoming changes in other PRs

- Re-generate commerce module references (for the updates in the method names)
- Ensure that the data model references are generated correctly for models using DML.
- (probably at a very later point) revisit recipes

www/apps/book/app/advanced-development/data-models/primary-key/page.mdx

@@ -0,0 +1,40 @@
+export const metadata = {
+  title: `${pageNumber} Data Model’s Primary Key`,
+}
+
+# {metadata.title}
+
+In this chapter, you’ll learn how to configure the primary key of a data model.
+
+## id Property
+
+A property defined with the `id` method is, by default, considered the data model’s primary key.
+
+---
+
+## primaryKey Method
+
+To set any `text` or `number` property as a primary key, use the `primaryKey` method.
+
+For example:
+
+export const highlights = [
+  ["4", "primaryKey", "Define the `code` property to be the data model's primary key."]
+]
+
+```ts highlights={highlights}
+import { model } from "@medusajs/utils"
+
+const MyCustom = model.define("my_custom", {
+  code: model.text().primaryKey(),
+  // ...
+})
+
+export default MyCustom
+```
+
+<Note>
+
+A property that’s defined with the `primaryKey` method takes precedence over an `id` property.
+
+</Note>