docs: extract "How to customize OpenAPI serving" into a guide

Co-authored-by: Hage Yaapa <[email protected]>
Signed-off-by: Miroslav Bajtoš <[email protected]>

docs/site/Server.md

@@ -69,40 +69,6 @@ const app = new RestApplication({
 });
 ```
 
-### Customize How OpenAPI Spec is Served
-
-There are a few options under `rest.openApiSpec` to configure how OpenAPI spec
-is served by the given REST server.
-
-- servers: Configure servers for OpenAPI spec
-- setServersFromRequest: Set `servers` based on HTTP request headers, default to
-  `false`
-- disabled: Set to `true` to disable endpoints for the OpenAPI spec. It will
-  disable API Explorer too.
-- endpointMapping: Maps urls for various forms of the spec. Default to:
-
-```js
-    {
-      '/openapi.json': {version: '3.0.0', format: 'json'},
-      '/openapi.yaml': {version: '3.0.0', format: 'yaml'},
-    }
-```
-
-```ts
-const app = new RestApplication({
-  rest: {
-    openApiSpec: {
-      servers: [{url: 'http://127.0.0.1:8080'}],
-      setServersFromRequest: false,
-      endpointMapping: {
-        '/openapi.json': {version: '3.0.0', format: 'json'},
-        '/openapi.yaml': {version: '3.0.0', format: 'yaml'},
-      },
-    },
-  },
-});
-```
-
 ### Configure the API Explorer
 
 LoopBack allows externally hosted API Explorer UI to render the OpenAPI

docs/site/guides/rest/customize-openapi.md

@@ -0,0 +1,48 @@
+---
+lang: en
+title: 'Customizing how OpenAPI spec is served'
+keywords: LoopBack 4.0, LoopBack 4, Node.js, OpenAPI, Customization
+sidebar: lb4_sidebar
+permalink: /doc/en/lb4/Customizing-how-openapi-spec-is-served.html
+---
+
+By default, LoopBack REST API server provides endpoints exposing an OpenAPI spec
+document describing application's API. You can configure this behavior using
+`rest.openApiSpec` field in the configuration object passed to `RestApplication`
+constructor.
+
+- servers: Configure servers for OpenAPI spec
+
+- setServersFromRequest: Set `servers` based on HTTP request headers, default to
+  `false`
+
+- disabled: Set to `true` to disable endpoints for the OpenAPI spec. It will
+  disable API Explorer too.
+
+- endpointMapping: Maps urls for various forms of the spec. Default to:
+
+  ```js
+  {
+    '/openapi.json': {version: '3.0.0', format: 'json'},
+    '/openapi.yaml': {version: '3.0.0', format: 'yaml'},
+  }
+  ```
+
+Example application configuration object showing possible customizations:
+
+{% include code-caption.html content="/src/index.ts" %}
+
+```ts
+const config: ApplicationConfig = {
+    rest: {
+    openApiSpec: {
+      servers: [{url: 'http://127.0.0.1:8080'}],
+      setServersFromRequest: false,
+      endpointMapping: {
+        '/openapi.json': {version: '3.0.0', format: 'json'},
+        '/openapi.yaml': {version: '3.0.0', format: 'yaml'},
+      },
+    },
+  };
+});
+```

docs/site/sidebars/lb4_sidebar.yml

@@ -181,6 +181,13 @@ children:
   output: 'web, pdf'
   children:
 
+  - title: 'Building REST APIs'
+    output: 'web, pdf'
+    children:
+    - title: 'Customizing how OpenAPI spec is served'
+      url: Customizing-how-openapi-spec-is-served.html
+      output: 'web, pdf'
+
   - title: 'Create Other Forms of APIs'
     url: Create-other-forms-of-apis.html
     output: 'web, pdf'