[Feature] Performer page notification badge/banner for duplicate performer based on URL matches

[echo6ix]

Is your feature request related to a problem? Please describe.
To identify existing duplicate performers when editing, and to mitigate the creation of duplicate performers via duplicate URL matching.

Describe the solution you'd like
When someone is creating or editing a performer, it would be extremely beneficial to sniffing out and mitigating duplicates by providing a visual notification of duplicate URLs matched against the entire database of URLs. Each URL field, existing or newly populated, would be scanned against the database URLs. Matches of duplicate URLs would be presented to the user for analysis.

Additional context
Sorry about the quality of the following mockup images. I am doing this very quick-and-dirty in Canva:

Image 1. Direct notification banner style. Could be reused for multiple types of notifications.

Image 2. Subtle notification badge adjacent to relevant tab.

Image 3. Notification icon beside duplicate link

This would also require a complimentary text blurb explaining the red notification icon

Additional note
This feature would especially be complimentary to any implementation of #821, because while extremely convenient, it could possibly increase the incidences of duplicate performer creation