Hello mkeiffer,
Thank you for reaching out to Apple Support Communities! It sounds like you're seeing a keychain pop-up on your Mac running macOS Catalina, and you're wondering how to prevent it. You're in the right place to find a resolution.
When you open Keychain Access on your Mac and type in 'searchpartyuseragent' using the search bar at the upper-right, are any items found? If so, select the item, then click on the information icon to view more details as shown here:
What is Keychain Access on Mac? - Apple Support
Searchparty items in Keychain Access can typically be related to iCloud features, such as Find My Mac. The 'com.apple.facetime: registrationV1' portion of that pop-up refers to your login information used for FaceTime (Apple ID and password). The Access Control tab of the information screen in Keychain Access allows you to further control app access to your FaceTime login. If 'searchpartyuseragent' shows it's related to iCloud features and functions in the information window, and you use the same Apple ID for both iCloud and FaceTime on your Mac, consider allowing it to have access.
Keep us posted on the results.
Cheers!