publisher: Decision record: Why Service sign in pages aren't linked to from transaction pages using a content id
Context
Currently, when content designers create a transaction page they enter a URL for the service that the start button should link to, and this service is usually an external (to GOV.UK) URL. Service sign in pages however will be GOV.UK content items, and ideally we should not link to specific content item URLs as they could change in future. Instead, the links should reference a content_id, which never changes. However as the field where content designers enter the URL that the start button should link to doesn't support content_ids currently, the only option available to them is to enter the URL for the service sign in page.
Decision
After discussing this with @kevindew from the publishing platform team, we identified that the risk of things breaking because we're linking directly to a URL is quite low because if the base_path of the service sign in page changes, the publishing API will automatically create a redirect.
Consequences
Ideally we should ensure that we're referencing the content_id instead of the service sign in page URL so that all risk is mitigated, so in future we should look at how we can support providing a content_id instead of a URL on the edit transaction page in Publisher.