[firestore-shorten-urls-dynamic-links] Regex validation on DYNAMIC_LINKS_URL_PREFIX

[joehan]

Expected Behavior

There should be some validationRegex for this parameter, since we know it should look likehttps://*.page.link

Actual Behavior

There isn't any validation. If you try to install with something invalid, the extension deploys correctly but sets shortUrl to undefined every time it triggers.

Specifications

• Extension name: firestore-shorten-urls-dynamic-links
• Version: 0.1.1

[jhuleatt]

FYI @kevinthecheung