feat(ls): provide OpenAPI 3.0.x Discriminator completion rules

Refs #2032

Author: char0n

packages/apidom-ls/src/config/openapi/discriminator/completion.ts

@@ -0,0 +1,36 @@
+import {
+  ApidomCompletionItem,
+  CompletionFormat,
+  CompletionType,
+} from '../../../apidom-language-types';
+
+const completion: ApidomCompletionItem[] = [
+  {
+    label: 'propertyName',
+    insertText: 'propertyName',
+    kind: 14,
+    format: CompletionFormat.QUOTED,
+    type: CompletionType.PROPERTY,
+    insertTextFormat: 2,
+    documentation: {
+      kind: 'markdown',
+      value:
+        '**REQUIRED**. The name of the property in the payload that will hold the discriminator value.',
+    },
+  },
+  {
+    label: 'mapping',
+    insertText: 'mapping',
+    kind: 14,
+    format: CompletionFormat.OBJECT,
+    type: CompletionType.PROPERTY,
+    insertTextFormat: 2,
+    documentation: {
+      kind: 'markdown',
+      value:
+        'Map[string, string]\n\\\n\\\nAn object to hold mappings between payload values and schema names or references.',
+    },
+  },
+];
+
+export default completion;

packages/apidom-ls/src/config/openapi/discriminator/meta.ts

@@ -1,7 +1,9 @@
+import completion from './completion';
 import documentation from './documentation';
 import { FormatMeta } from '../../../apidom-language-types';
 
 const meta: FormatMeta = {
+  completion,
   documentation,
 };