New header and primary navigation for candidate support and provider

[CatalinVoineag]

Context

New header design proposed

With the introduction of one login and the fact that we need a new
header and primary navigation for the candidate path, to allow the
candidate to manage their one login account.

We decided to implement the header and primary navigation for our other users.
providers and support as well as candidates.

I have not changed these components for our api users. The content
that's already there needs a bit more work before, I think.

This should show the GOV.UK One Login account link for candidates if the
one login feature is enabled.

I could have gone down the rabbit hole of refactoring the code for our headers.
I think we can really simplify how we do them but I don't think this is the PR/ticket to do it.

Changes proposed in this pull request

_header.html.erb partial
navigation helper
CSS changes to allow the govuk components to align links on the right
Specs to accommodate the new header

Guidance to review

Screencast.2025-01-15.10.36.25.mp4

Go onto QA or review and please have a look at the header and the primary navigation at the top for all our users. Candidate, Provider, Support.

Bonus points if you change your one login account password and try to login again.

Link to Trello card

https://trello.com/c/weh5myMB

Things to check

• If the code removes any existing feature flags, a data migration has also been added to delete the entry from the database
• This code does not rely on migrations in the same Pull Request
• If this code includes a migration adding or changing columns, it also backfills existing records for consistency
• If this code adds a column to the DB, decide whether it needs to be in analytics yml file or analytics blocklist, if included inform data insights team of the changes
• If this code adds a column that may include PII, the sanitise.sql script and 0025-protecting-personal-data-in-production-dump.md ADR have been updated.
• API release notes have been updated if necessary
• If it adds a significant user-facing change, is it documented in the CHANGELOG?
• Attach the PR to the Trello card

[CatalinVoineag]

This is copied straight from the one login header component https://github.com/govuk-one-login/service-header

With minor changes to make it fit in our header, the width and height are reduced

[CatalinVoineag]

The changes in this file are mostly to switch to using govuk_service_navigation instead of PrimaryNavigationComponent

And changing the HeaderComponent params, we don't need a service name or product name

[CatalinVoineag]

The logic in this file is the same, just changed the format to allow us to use govuk-service-navigation

[CatalinVoineag]

I didn't find another way to pass the SVG to the govuk-service-navigation so we have to call html_safe here with a string of the svg

[elceebee]

I've tested on qa and it seems fine! nice work