docs: add ModuleWithProviders migration doc (angular#33085)

PR Close angular#33085

.github/CODEOWNERS

@@ -455,6 +455,7 @@
 # ================================================
 
 /packages/compiler-cli/ngcc/**                                  @angular/fw-ngcc @angular/framework-global-approvers
+/aio/content/guide/ngcc.md                                      @angular/fw-ngcc @angular/framework-global-approvers
 
 
 
@@ -885,6 +886,7 @@ testing/**                                                      @angular/fw-test
 /aio/content/guide/migration-dynamic-flag.md                    @angular/fw-docs-packaging @angular/framework-global-approvers @angular/framework-global-approvers-for-docs-only-changes
 /aio/content/guide/migration-injectable.md                      @angular/fw-docs-packaging @angular/framework-global-approvers @angular/framework-global-approvers-for-docs-only-changes
 /aio/content/guide/migration-localize.md                        @angular/fw-docs-packaging @angular/framework-global-approvers @angular/framework-global-approvers-for-docs-only-changes
+/aio/content/guide/migration-module-with-providers.md           @angular/fw-docs-packaging @angular/framework-global-approvers @angular/framework-global-approvers-for-docs-only-changes
 
 
 # ================================================

aio/content/guide/deprecations.md

@@ -362,6 +362,10 @@ See the [dedicated migration guide for adding missing `@Injectable` decorators](
 
  See the [dedicated migration guide for `$localize`](guide/migration-localize).
 
+{@a module-with-providers}
+### Migrating `ModuleWithProviders`
+
+ See the [dedicated migration guide for `ModuleWithProviders`](guide/migration-module-with-providers).
 
 
 {@a removed}

aio/content/guide/migration-module-with-providers.md

@@ -0,0 +1,78 @@
+# `ModuleWithProviders` Migration
+
+## What does this schematic do?
+
+
+Some Angular libraries, such as `@angular/router` and `@ngrx/store`, implement APIs that return a type called `ModuleWithProviders` (typically via a method named `forRoot()`).
+This type represents an `NgModule` along with additional providers.
+Angular version 9 deprecates use of `ModuleWithProviders` without an explicitly generic type, where the generic type refers to the type of the `NgModule`.
+
+This schematic will add a generic type to any `ModuleWithProviders` usages that are missing the generic.
+In the example below, the type of the `NgModule` is `SomeModule`, so the schematic changes the type to be `ModuleWithProviders<SomeModule>`.
+
+
+**Before**
+```ts
+
+@NgModule({...})
+export class MyModule {
+  static forRoot(config: SomeConfig): ModuleWithProviders {
+    return {
+      ngModule: SomeModule,
+      providers: [
+        {provide: SomeConfig, useValue: config}
+      ]
+    };
+  }
+}
+
+```
+
+**After**
+
+```ts
+@NgModule({...})
+export class MyModule {
+  static forRoot(config: SomeConfig): ModuleWithProviders<SomeModule> {
+    return {
+      ngModule: SomeModule,
+      providers: [
+        {provide: SomeConfig, useValue: config }
+      ]
+    };
+  }
+}
+```
+
+In the rare case that the schematic can't determine the type of `ModuleWithProviders`, you may see the schematic print a TODO comment to update the code manually.
+
+
+## Why is this migration necessary?
+
+`ModuleWithProviders` has had the generic type since Angular version 7, but it has been optional.
+This has compiled because the `metadata.json` files contained all the metadata.
+With Ivy, `metadata.json` files are no longer required, so the framework cannot assume that one with the necessary types has been provided.
+Instead, Ivy relies on the generic type for `ModuleWithProviders` to get the correct type information.
+
+For this reason, Angular version 9 deprecates `ModuleWithProviders` without a generic type.
+A future version of Angular will remove the default generic type, making an explicit type required.
+
+## Should I add the generic type when I add new `ModuleWithProviders` types to my application?
+
+Yes, any time your code references the `ModuleWithProviders` type, it should have a generic type that matches the actual `NgModule` that is returned (for example, `ModuleWithProviders<MyModule>`).
+
+
+## What should I do if the schematic prints a TODO comment?
+
+The schematic will print a TODO comment in the event that it cannot detect the correct generic for the `ModuleWithProviders` type.
+In this case, you'll want to manually add the correct generic to `ModuleWithProviders`. It should match the type of whichever `NgModule` is returned in the `ModuleWithProviders` object.
+
+## What does this mean for libraries?
+
+Libraries should add the generic type to any usages of the `ModuleWithProviders` type.
+
+
+## What about applications using non-migrated libraries?
+
+`ngcc` should transform any non-migrated libraries to generate the proper code.
+For more information on `ngcc` see the [ngcc guide](guide/ngcc).

aio/content/guide/ngcc.md

@@ -0,0 +1,7 @@
+
+# `ngcc`
+
+## What is `ngcc`?
+
+The Angular Compatibility Compiler, or `ngcc`, is a process that the CLI automatically runs which compiles all your libraries with Ivy.
+This means that even if the libraries your app depends on don't use Ivy, `ngcc` will update them to use Ivy for you.

aio/content/navigation.json

@@ -744,6 +744,11 @@
           "title": "Usage Analytics",
           "tooltip": "For administrators, guide to gathering usage analytics from your users.",
           "url": "cli/usage-analytics-gathering"
+        },
+        {
+          "title": "ngcc",
+          "tooltip": "Description of the Angular Compatibility Compiler.",
+          "url": "guide/ngcc"
         }
       ]
     },