AO3-7398 Add username to Challenge Sign-Ups browser page title

[lynnhaotran]

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Issue

https://otwarchive.atlassian.net/browse/AO3-7398

Purpose

This PR fixes the browser page title for "Challenge Sign-Ups" to include the username of the logged in user if the user is looking at their own sign-up page (based on my understanding of the existing code a user should only be able to look at their own sign-ups page, but let me know if I've misinterpreted this.)

Credit

lynn (she/her) - but my username is also fine! thanks :-)

[sarken]

Hi, lynn!

Thank you so much for this pull request. Someone will be along to review it soon.

In the meantime, we're updated the Jira issue status to In Review so no one mistakenly creates a duplicate pull request. If you'd like the ability to comment on, assign, and transition issues in the future, you're welcome to create a Jira account! It makes things a bit easier for us on the organizational side if the Full Name on your Jira account either closely matches the name you'd like us to credit in the release notes or includes it in parentheses, e.g. "Nickname (CREDIT NAME)."

Once you've done that (or if you've already done it -- Jira has been unreliable about showing us new accounts in the admin panel lately), you can either reply here or send an email to otw-coders@transformativeworks.org with your account name and email address and we'll set up the permissions for you.

Thanks again for contributing! If you have any questions, you can contact us at the same email address listed above.

[Bilka2]

Thank you!