List personal access tokens for service accounts

What does this MR do and why?

For service accounts, list personal access tokens.

This is work in progress. Future work:

• Update URL when filters are modified
• Add cards summarising some stats: number of active/inactive/expiring soon tokens
• Add sorting options
• Enable revoking/rotation of tokens

EE: true

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• #515340 (closed)

MR acceptance checklist

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Screenshots or screen recordings

Empty state	Tokens and filters	Tokens with long descriptions

Viewport size
xs (<576px)
sm (>=576px)
md (>=768px)
lg (>=992px)
xl (>=1200px)

How to set up and validate locally

1. Enable the following feature flag: https://gdk.test:3443/rails/features/service_accounts_crud
2. Enable Ultimate license to group Flightjs
3. Create a service account and several tokens in the gdk rails console:

group = Group.find_by(name: 'Flightjs')
response = Namespaces::ServiceAccounts::CreateService.new(User.first, name: 'My service account', organization_id: group.organization_id, namespace_id: group.id).execute
service_account = response.payload[:user]

(1..5).each do |n|
  service_account.personal_access_tokens.create!(name: "Active token #{n}", expires_at: 30.days.since, scopes: ['read_api', 'read_user'])

  service_account.personal_access_tokens.create!(name: "Expiring token #{n}", expires_at: 5.days.since, scopes: ['read_api', 'read_user'])

  service_account.personal_access_tokens.create!(name: "Expired token #{n}", expires_at: 30.days.ago, scopes: ['read_api', 'read_user'])

  service_account.personal_access_tokens.create!(name: "Revoked token #{n}", revoked: true, expires_at: 30.days.since, scopes: ['read_api', 'read_user'])
end

service_account.id

4. In SaaS emulation, go to https://gdk.test:3443/groups/my_service_account/-/settings/service_accounts/[id (last line from console)]/access_tokens
5. Without SaaS emulation, go to https://gdk.test:3443/admin/application_settings/service_accounts/[id (last line from console)]/access_tokens