docs(lb4): repository-json-schema docs

pages/en/lb4/Decorators.md

@@ -378,7 +378,7 @@ For more information, see the [Dependency Injection](Dependency-Injection.htm) s
 
 #### Property Decorator
 
-  Syntax: `@property(definition: PropertyDefinition)`
+  Syntax: `@property(definition?: PropertyDefinition)`
 
   The property decorator defines metadata for a property on a Model definition.
   The format of property definitions can be found in [Property definitions](https://loopback.io/doc/en/lb2/Model-definition-JSON-file.html#properties)

pages/en/lb4/Implementing-features.md

@@ -243,18 +243,17 @@ LoopBack is agnostic when it comes to accessing databases. You can choose any pa
     export class Product extends Entity {
       @property({
         description: 'The unique identifier for a product',
-        type: 'number',
         id: true,
       })
       id: number;
 
-      @property({type: 'string', required: true})
+      @property({required: true})
       name: string;
 
-      @property({type: 'string', required: true})
+      @property({required: true})
       slug: string;
 
-      @property({type: 'number', required: true})
+      @property({required: true})
       price: number;
 
       // Add the remaining properties yourself:

pages/en/lb4/Repositories.md

@@ -65,10 +65,10 @@ import {Entity, model, property} from '@loopback/repository';
 
 @model()
 export class Account extends Entity {
-  @property({type: 'number', id: true})
+  @property({id: true})
   id: number;
 
-  @property({type: 'string', required: true})
+  @property({required: true})
   name: string;
 }
 ```

pages/en/lb4/Schemas.md

@@ -144,6 +144,76 @@ class Customer extends Entity {
 }
 ```
 
+### JSON Schema inference
+With type information inferred from using `@model` and `@property` decorators,
+we've created a module to easily build a JSON Schema from a decorated model.
+In the `@loopback/repository-json-schema` module, we provide `getJsonSchema`
+which accesses the metadata stored by the decorators to build a matching
+JSON Schema of your model.
+
+```ts
+import {model, property} from '@loopback/repository';
+import {getJsonSchema} from '@loopback/repository-json-schema';
+
+@model()
+class Category {
+  @property() name: string;
+}
+
+@model()
+class Product {
+  @property({required: true}) name: string;
+  @property() type: Category;
+}
+
+const jsonSchema = getJsonSchema(Product);
+```
+
+`jsonSchema` from above would return:
+
+```json
+{
+  "title": "Product",
+  "properties": {
+    "name": {
+      "type": "string"
+    },
+    "type": {
+      "$ref": "#/definitions/Category"
+    }
+  },
+  "definitions": {
+    "Category": {
+      "properties": {
+        "name": {
+          "type": "string"
+        }
+      }
+    }
+  },
+  "required": ["name"]
+}
+```
+
+If a custom type is specified for a decorated property in a model definition, then 
+a reference [`$ref`](http://json-schema.org/latest/json-schema-core.html#rfc.section.8)
+field is created for it and a `definitions` sub-schema is created at the top-level
+of the schema and populated with the type definition by recursively calling
+`getJsonSchema` to build its properties. This allows for complex and nested custom
+type definition building. The example above illustrates this point by having the
+custom type `Category` as a property of our `Product` model definition. 
+
+#### Supported JSON keywords
+Following are the supported keywords that can be explicitly passed into the decorators
+to better tailor towards the JSON Schema being produced.
+
+| Keywords    | Decorator   | Type    | Default      | Description                                             |
+|-------------|-------------|---------|--------------|---------------------------------------------------------|
+| title       | `@model`    | string  | *model name* | Name of the model                                       |
+| description | `@model`    | string  |              | Description of the model                                |
+| array       | `@property` | boolean |              | Used to specify whether the property is an array or not |
+| required    | `@property` | boolean |              | Used to specify whether the property is required or not |
+
 ## Other ORMs
 You might decide to use an alternative ORM/ODM in your LoopBack application.
 Loopback v4 no longer expects you to provide your data in its own custom Model