The documentation (https://developer.apple.com/documentation/BundleResources/Entitlements/com.apple.developer.associated-domains)
for a message filter extension says:
If you use a private web server, which is unreachable from the public internet, while developing your app, enable the alternate mode feature to bypass the CDN and connect directly to your server.
<service>:<fully qualified domain>?mode=<alternate mode>
Where alternate mode is one of the following:
developer
Specifies that only devices in developer mode can access the domain. In this mode, you can use any valid SSL certificate on your web server, including a certificate that the system doesn’t trust.
What does it mean "you can use any valid SSL certificate on your web server"?
Does the app have to do anything with regards to this?