Add domain verification operation views

Related issue #375492 (closed)

What does this MR do and why?

Add domain verification operation views.

The feature is under feature flag: domain_verification_operation

The haml views are copy from app/views/projects/pages_domains/. The main differences:

• Add a new project select component in create form
• UI changed(design link) and follow the new Pajamas design system
• Action link url changed
• Need add new documentation page replace the doc link

dependent MRs:

• !116641 (merged)
• !116626 (merged)

design link Figma

/cc @daveliu @qk44077907

Screenshots or screen recordings

Empty index page	Index page with domains

New domain page

Edit domain page

How to set up and validate locally

1. simulate the SaaS locally:

   export GITLAB_SIMULATE_SAAS=1

2. Upload Premium license to enable domain_verification feature

3. Enable pages in gitlab.yml:

   pages:
     enabled: true
     access_control: false
     host: example.com
     port: 80
     external_http: true
     external_https: true

4. enable domain_verification_operation feature in console:

   Feature.enable(:domain_verification_operation)

5. Change application settings in rails console:

   ApplicationSetting.current.update(pages_domain_verification_enabled: true, lets_encrypt_terms_of_service_accepted: true, 
   lets_encrypt_notification_email: "test@gitlab.com")

6. Visit domain verification page http://localhost:3000/groups/flightjs/-/settings/domain_verification

7. Click the Add Domain button.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

doc/user/enterprise_user/index.md

@@ -46,21 +46,22 @@ Prerequisites:
 
 Setting up a verified domain is similar to [setting up a custom domain on GitLab Pages](../project/pages/custom_domains_ssl_tls_certification/index.md). However, you must:
 
-- Require link domain to a project. [For Future direction about group-level domain verification.](https://gitlab.com/groups/gitlab-org/-/epics/5299)
+- Link the domain to a project. For more information on group-level domain verification, see [issue 5299](https://gitlab.com/groups/gitlab-org/-/epics/5299).
 - Configure the DNS `TXT` record to verify the domain's ownership.
 
 Steps:
 
 #### 1. Add a custom domain for the matching email domain
 
-The domain must match the email domain exactly. For example, if your email is `username@example.com`, verify the `example.com` domain.
+The custom domain must match the email domain exactly. For example, if your email is `username@example.com`, verify the `example.com` domain.
 
 1. On the top bar, select **Main menu > Groups** and find your top group.
 1. On the left sidebar, select **Settings > Domain Verification**.
 1. In the upper-right corner, select **Add Domain**.
 1. In **Domain**, enter the domain name.
 1. In **Project**, link to a project.
-1. Optional. In **Certificate**, switch the **Manually enter certificate information** toggle to add an SSL/TLS certificate. You can also add the certificate and key later.
+1. Optional. In **Certificate**, switch the **Manually enter certificate information** toggle to add an SSL/TLS
+   certificate. You can also add the certificate and key later.
 1. Select **Add Domain**.
 
 #### 2. Get a verification code
@@ -72,7 +73,7 @@ and paste them in your domain's control panel as a `TXT` record.
 
 #### 3. Verify the domain's ownership
 
-Once you have added all the DNS records:
+After you have added all the DNS records:
 
 1. On the top bar, select **Main menu > Groups** and find your group.
 1. On the left sidebar, select **Settings > Domain Verification**.
@@ -81,8 +82,8 @@ Once you have added all the DNS records:
 ![Verify your domain](../img/retry_domain_verification_v16_0.png)
 
 WARNING:
-Considering GitLab instances with domain verification enabled,
-if the domain can't be verified for 7 days, it's removed
+For GitLab instances with domain verification enabled,
+if the domain cannot be verified for 7 days, that domain removed
 from the GitLab project.
 
 > **Notes:**