[CL-135] CL migration docs (#6535)

libs/components/src/stories/migration.mdx

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+import { Meta } from "@storybook/addon-docs";
+
+<Meta title="Documentation/Migration" />
+
+# Migrating to the Component Library
+
+You have been tasked with migrating a component to use the CL. What does that entail?
+
+## Getting Started
+
+Before progressing here, please ensure that...
+
+- You have fully setup your dev environment as described in the
+  [contributing docs](https://contributing.bitwarden.com/).
+- You are familiar with [Angular reactive forms](https://angular.io/guide/reactive-forms).
+- You are familiar with [Tailwind](https://tailwindcss.com/docs/utility-first).
+
+## Background
+
+The design of Bitwarden is in flux. At the time of writing, the frontend codebase uses a mix of
+multiple UI frameworks: Bootstrap, custom "box" styles, and this component library, which is built
+on top of Tailwind. In short, the "CL migration" is a move to only use the CL and remove everything
+else.
+
+This is very important work. Centralizing around a shared design system will:
+
+- improve user experience by utilizing consistent patterns
+- improve developer experience by reducing custom complex UI code
+- improve dev & design velocity by having a central location to make UI/UX changes that impact the
+  entire project
+
+## Success Criteria
+
+Follow these steps to fully migrate a component.
+
+### Use Storybook
+
+Don't recreate the wheel.
+
+After reviewing a design, consult this Storybook to determine if there is a component built for your
+usecase. Don't waste effort styling a button or building a popover menu from scratch--we already
+have those. If a component isn't flexible enough or doesn't exist for your usecase, contact Will
+Martin.
+
+### Use Tailwind
+
+Only use Tailwind for styling. No Bootstrap or other custom CSS is allowed.
+
+This is easy to verify. Bitwarden prefixes all Tailwind classes with `tw-`. If you see a class
+without this prefix, it probably shouldn't be there.
+
+<div class="tw-bg-danger-500/10 tw-p-4">
+  <span class="tw-font-bold tw-text-danger">Bad (Bootstrap)</span>
+  ```html
+  <div class="mb-2"></div>
+  ```
+</div>
+
+<div class="tw-bg-success-500/10 tw-p-4">
+  <span class="tw-font-bold tw-text-success">Good (Tailwind)</span>
+  ```html
+  <div class="tw-mb-2"></div>
+  ```
+</div>
+
+**Exception:** Icon font classes, prefixed with `bwi`, are allowed.
+
+<div class="tw-bg-success-500/10 tw-p-4">
+  <span class="tw-font-bold tw-text-success">Good (Icons)</span>
+  ```html
+  <i class="bwi bwi-spinner bwi-lg bwi-spin" aria-hidden="true"></i>
+  ```
+</div>
+
+### Use Reactive Forms
+
+The CL has form components that integrate with Angular's reactive forms: `bit-form-field`,
+`bitSubmit`, `bit-form-control`, etc. All forms should be migrated from template-drive forms to
+reactive forms to make use of these components. Review the
+[form component docs](?path=/docs/component-library-form--docs).
+
+<div class="tw-bg-danger-500/10 tw-p-4">
+    <span class="tw-text-danger tw-font-bold">Bad</span>
+    ```html
+    <form #form (ngSubmit)="submit()">
+        ...
+    </form>
+    ```
+</div>
+
+<div class="tw-bg-success-500/10 tw-p-4">
+    <span class="tw-text-success tw-font-bold">Good</span>
+    ```html
+    <form [formGroup]="formGroup" [bitSubmit]="submit">
+        ...
+    </form>
+    ```
+</div>
+
+### Dialogs
+
+Legacy Bootstrap modals use the `ModalService`. These should be converted to use the `DialogService`
+and it's [related CL components](?path=/docs/component-library-dialogs--docs). Components that are
+fully migrated should have no reference to the `ModalService`.
+
+1. Update the template to use CL components:
+
+<div class="tw-bg-danger-500/10 tw-p-4">
+    ```html
+    <!-- FooDialogComponent -->
+    <div class="modal fade" role="dialog" aria-modal="true">...</div>
+    ```
+</div>
+
+<div class="tw-bg-success-500/10 tw-p-4">
+    ```html
+    <!-- FooDialogComponent -->
+    <bit-dialog>...</bit-dialog>
+    ```
+</div>
+
+2. Create a static `open` method on the component, that calls `DialogService.open`:
+
+<div class="tw-bg-success-500/10 tw-p-4">
+    ```ts
+      export class FooDialogComponent {
+        //...
+
+        static open(dialogService: DialogService) {
+          return dialogService.open(DeleteAccountComponent);
+        }
+      }
+    ```
+
+</div>
+
+3. If you need to pass data into the dialog, pass it to `open` as a parameter and inject
+   `DIALOG_DATA` into the component's constructor.
+
+<div class="tw-bg-success-500/10 tw-p-4">
+    ```ts
+    export type FooDialogParams = {
+      bar: string;
+    }
+
+    export class FooDialogComponent {
+      constructor(@Inject(DIALOG_DATA) protected params: FooDialogParams) {}
+
+      static open(dialogService: DialogService, data: FooDialogParams) {
+        return dialogService.open(DeleteAccountComponent, { data });
+      }
+    }
+    ```
+
+</div>
+
+4. Replace calls to `ModalService.open` or `ModalService.openViewRef` with the newly created static
+   `open` method:
+
+<div class="tw-bg-danger-500/10 tw-p-4">`this.modalService.open(FooDialogComponent);`</div>
+
+<div class="tw-bg-success-500/10 tw-p-4">`FooDialogComponent.open(this.dialogService);`</div>
+
+## Examples
+
+The following examples come from accross the Bitwarden codebase.
+
+### 1.) AboutComponent
+
+Codeowner: Platform
+
+https://github.com/bitwarden/clients/pull/6301/files
+
+This migration updates a `ModalService` component to the `DialogService`.
+
+**Note:** Most of the internal markup of this component was unchanged, aside from the removal of
+defunct Bootstrap classes.
+
+### 2.) Auth
+
+Codeowner: Auth
+
+https://github.com/bitwarden/clients/pull/5377
+
+This PR also does some general refactoring, the main relevant change can be seen here:
+
+[Old template](https://github.com/bitwarden/clients/pull/5377/files#diff-4fcab9ffa4ed26904c53da3bd130e346986576f2372e90b0f66188c809f9284d)
+-->
+[New template](https://github.com/bitwarden/clients/pull/5377/files#diff-cb93c74c828b9b49dc7869cc0324f5f7d6609da6f72e38ac6baba6d5b6384327)
+
+Updates a dialog, similar to example 1, but also adds CL form components and Angular Reactive Forms.
+
+### 3.) AC
+
+Codeowner: Admin Console
+
+https://github.com/bitwarden/clients/pull/5417
+
+Migrates dialog, form, buttons, and a table.
+
+### 4.) Vault
+
+Codeowner: Vault
+
+https://github.com/bitwarden/clients/pull/5648
+
+Some of our components are shared between multiple clients (web, desktop, and the browser extension)
+through the use of inheritance. This PR updates the _web_ template of a cross-client component to
+use Tailwind and the CL, and updates the base component implementation to use reactive forms,
+without updating the desktop or browser templates.
+
+## Questions
+
+Please direct any development questions to Will Martin. Thank you!