Add Gen 2 SDL docs (#7793)

* add gen 2 SDL docs

* Update src/pages/[platform]/build-a-backend/data/data-modeling/index.mdx

Co-authored-by: josef <josef.aidt@gmail.com>

* Update src/pages/[platform]/build-a-backend/data/data-modeling/index.mdx

Co-authored-by: josef <josef.aidt@gmail.com>

* move support callout to migration page

* update doc to state ddb-backed sources only

* made updates to the sdl explanation

---------

Co-authored-by: josef <josef.aidt@gmail.com>
Co-authored-by: Nikhil Swaminathan <nikhil@live.ca>

Author: 3 people

src/pages/[platform]/build-a-backend/data/data-modeling/index.mdx

@@ -32,6 +32,7 @@ export function getStaticProps(context) {
   };
 }
 
+## Data modeling capabilities
 
 Every data model is defined as part of a data schema (`a.schema()`). You can enhance your data model with various fields, customize their identifiers, apply authorization rules, or model relationships. Every data model (`a.model()`) automatically provides create, read, update, and delete API operations as well as real-time subscription events. Below is a quick tour of the many functionalities you can add to your data model:
 
@@ -84,3 +85,34 @@ export const data = defineData({
 ```
 
 <Overview childPageNodes={props.childPageNodes} />
+
+## Gen 1 schema support 
+
+If you are coming from Gen 1, you can continue to use the GraphQL Schema Definition Language (SDL) for defining your schema. However, we strongly recommend you use the TypeScript-first schema builder experience in your project as it provides type safety and is the recommended way of working with Amplify going forward.
+
+<Callout>
+
+**Note:** Some features available in Gen 1 GraphQL SDL are not available in Gen 2. See the [feature matrix](/[platform]/start/migrate-to-gen2/#gen-1-vs-gen-2-feature-matrix) for features supported in Gen 2.
+
+</Callout>
+
+```ts title="amplify/data/resource.ts"
+import { defineData } from '@aws-amplify/backend';
+
+const schema = /* GraphQL */`
+  type Todo @model @auth(rules: [{ allow: owner }]) {
+    content: String
+    isDone: Boolean
+  }
+`;
+
+export const data = defineData({
+  schema,
+  authorizationModes: {
+    defaultAuthorizationMode: "apiKey",
+    apiKeyAuthorizationMode: {
+      expiresInDays: 30,
+    },
+  },
+});
+```

src/pages/[platform]/start/migrate-to-gen2/index.mdx

@@ -41,7 +41,7 @@ The tables below present a feature matrix for Gen 1 customers who are considerin
 ### Auth
 
 | Feature | Gen 1 | Gen 2 |
-|---|---|---| 
+|---|---|---|
 | Configure username | Yes | Yes with CDK |
 | Configure email | Yes | Yes |
 | Configure phone number | Yes | Yes |
@@ -92,7 +92,7 @@ The tables below present a feature matrix for Gen 1 customers who are considerin
 | hasOne | Yes | Yes |
 | hasMany | Yes | Yes |
 | belongsTo | Yes | Yes |
-| manyToMany | Yes | Yes |
+| manyToMany | Yes | No |
 | default | Yes | Yes |
 | **auth - model level** |   |   |
 | auth - public - apiKey | Yes | Yes |
@@ -143,6 +143,8 @@ The tables below present a feature matrix for Gen 1 customers who are considerin
 | Custom GraphQL Transformer plugins | Yes | No |
 | MySQL and PostgreSQL support | No | Yes |
 | In-IDE end-to-end type safety | No | Yes |
+| @hasOne, @hasMany, and @belongsTo on required fields | Yes | No |
+| fields argument on @hasOne, @hasMany, and @belongsTo | Yes | No |
 
 ### Storage
 
@@ -200,7 +202,7 @@ The tables below present a feature matrix for Gen 1 customers who are considerin
 <InlineFilter filters={['android', 'swift']}>
 
 | Feature | Gen 1 | Gen 2 |
-|---|---|---| 
+|---|---|---|
 | REST API| Yes|	No
 | Analytics| Yes|	Yes with custom CDK
 | Geo| Yes|	Yes with custom CDK
@@ -212,7 +214,7 @@ The tables below present a feature matrix for Gen 1 customers who are considerin
 <InlineFilter filters={['flutter']}>
 
 | Feature | Gen 1 | Gen 2 |
-|---|---|---| 
+|---|---|---|
 | REST API| Yes|	Yes with custom CDK
 | Analytics| Yes|	Yes with custom CDK
 | Geo| No|	No
@@ -224,7 +226,7 @@ The tables below present a feature matrix for Gen 1 customers who are considerin
 <InlineFilter filters={['angular','javascript','nextjs','react','react-native','vue']}>
 
 | Feature | Gen 1 | Gen 2 |
-|---|---|---| 
+|---|---|---|
 | REST API| Yes|	Yes with custom CDK
 | Analytics| Yes|	Yes with custom CDK
 | Geo| Yes|	Yes with custom CDK