Add clarification on parent agency in Identifier component

[thisisdano]

Summary

Added clarification on parent agency in Identifier component. The identifier can be used by any site, regardless of whether that site has a higher-level agency associated with it. For this component, “Parent agency” means "the highest-level agency associated with a site or service." This PR adds guidance to cover cases when a site is the primary site for an agency, and has no higher-level agency.

Related issue

Closes #2592

Preview link

Preview link: Identifier page →

Problem statement

Not every site has a parent agency. In some cases, a site or service is the primary site for an agency. (For example, dhs.gov is the primary site for the Department of Homeland Security. It does not have a "parent agency.") Our current guidance suggests that if a site doesn't have a parent agency, they shouldn't use the identifier. But this is not the case. Every site can use the identifier.

Our guidance should make it more clear that every site can use the identifier. When we talk about "parent agency," it's a simpler way of saying "the highest-level agency associated with a site or service."

Solution

This PR makes a couple additions to our identifier guidance.

1. Add more inclusive language to the "When to use the identifier component" section:

To identify highest-level agency associated with a site or service. The identifier is a complement to the USWDS banner. Use the identifier to tell users what agency is responsible for your website. If your site is the primary site associated with an agency, you can still use the identifier. Consider the parent agency to be the highest-level agency associated with a site or service.

2. Add a clarification to the "Usability guidance" section:

Consider the parent agency to be the highest-level agency associated with a site or service. In some cases, your site may not have a parent agency. If your site is the primary site for your agency, use your agency name in place of [Parent Agency]. For example, “[agency.gov] An official website of [Agency].”

I do not suggest making a change to the component's dek: "The identifier communicates a site’s parent agency and displays agency links required by federal laws and policies." Most sites and services using the design system will have a parent agency, and the plain-language benefit to using "parent agency" in the dek may outweigh the clarity gained with the wordier phrasing.

Major changes

None

Testing and review

1. Verify noted changes to the "When to use this component" section.
2. Verify noted changes to the "Usability guidance" section.
3. Check that the changelog accurately captures the nature of these clarifications.
4. Check for spelling, grammar, plain language, and correctness.
5. Check that there aren't any other places on this page that need a clarification.