[macos]: packaged apps not acceptable to the app store

A DESCRIPTION OF THE PROBLEM :
Packaged app run, but there are still issues with submission to the app store, specifically
with info.plist contents and with code signing.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
build with jpackage
package with productbuild
submit to app store


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
acceptance

ACTUAL -
Here is the error summary I got from the app store after my best effort to supply a valid
package from a .app packaged by jpackage
Dear Developer,

We identified one or more issues with a recent delivery for your app, "Boardspace.net Launcher" 1.0.13 (1.0.13). Please correct the following issues, then upload again.

ITMS-90249: The product archive is invalid - The value of the LSApplicationCategoryType key in the Info.plist is Unknown, which is not a UTI for a valid category. For more details, see 'Submitting your Mac apps to the App Store'.

ITMS-90296: App sandbox not enabled - The following executables must include the 'com.apple.security.app-sandbox' entitlement with a Boolean value of true in the entitlements property list: [( 'com.boardspace.launcher.pkg/Payload/boardspace.app/Contents/MacOS/boardspace', 'com.boardspace.launcher.pkg/Payload/boardspace.app/Contents/runtime/Contents/Home/lib/jspawnhelper' )] Refer to App Sandbox page at https://developer.apple.com/documentation/security/app_sandbox for more information on sandboxing your app.


CUSTOMER SUBMITTED WORKAROUND :
you can skip the signing and manually edit the .plist file to fix the plist, but the
signing problems with the pre-signed components are not fixable by me AFAIK
For the plist, it would be handy to be able to pass a prototype plist.

Also, the plist "minim system version" ought to be settable.


FREQUENCY : always