Fix for login url for missing records

[joachimnielandt]

When opening a missing (or unavailable to you) record, the alert is potentially directing you to a wrong login location. This is noticeable on our fork (we use the openid security flow), where if you click the link the redirection lands you on the basic auth login form which is disabled at that point.

The fix seems to be consistent for both basic auth and openid, following the same url setup as is used in menu-signin.html.

Before the fix, the link points to /catalog.signin. Afterwards, it points to /signin, which falls back to the basic auth login form correctly if necessary.

Checklist

• I have read the contribution guidelines
• Pull request provided for main branch, backports managed with label
• Good housekeeping of code, cleaning up comments, tests, and documentation
• Clean commit history broken into understandable chucks, avoiding big commits with hundreds of files, cautious of reformatting and whitespace changes
• Clean commit messages, longer verbose messages are encouraged
• API Changes are identified in commit messages
• Testing provided for features or enhancements using automatic tests
• User documentation provided for new features or enhancements in manual
• Build documentation provided for development instructions in README.md files
• Library management using pom.xml dependency management. Update build documentation with intended library use and library tutorials or documentation