Add codegen_name annotations to ManagedBy (#2368)

Author: swallez

.github/workflows/validate-pr.yml

@@ -18,7 +18,7 @@ jobs:
     if: github.repository_owner == 'elastic' # this action will fail if executed from a fork
     runs-on: ubuntu-latest
     env:
-      STACK_VERSION: 8.10-SNAPSHOT
+      STACK_VERSION: 8.13-SNAPSHOT
 
     steps:
       - uses: actions/checkout@v2

output/schema/schema.json

@@ -30,8 +30,11 @@ import { integer } from '@_types/Numeric'
 import { DataStreamLifecycleWithRollover } from '@indices/_types/DataStreamLifecycle'
 
 enum ManagedBy {
+  /** @codegen_name ilm */
   'Index Lifecycle Management',
+  /** @codegen_name datastream */
   'Data stream lifecycle',
+  /** @codegen_name unmanaged */
   'Unmanaged'
 }