Document certificate upload for macOS

[ann0see]

Describe the bug

The current state of the signing workflow is confusing. Names don't match. Also the App Store certs are weird.
This should all be documented.

To Reproduce
Update the signing certificates for macOS signing.

See the mapping:

          MACOS_CERTIFICATE:        ${{ secrets.MACOS_CERT }} # Base64 encoded Developer ID Application certificate. See https://help.apple.com/xcode/mac/current/#/dev154b28f09
          MACOS_CERTIFICATE_PWD:    ${{ secrets.MACOS_CERT_PWD }} # Password protecting secrets.MACOS_CERTIFICATE
          MACOS_CERTIFICATE_ID:     ${{ secrets.MACOS_CERT_ID }} # Certificate ID of secrets.MACOS_CERTIFICATE. If unknown, import secrets.MACOS_CERT into keychain and get the hash via "security find-identity -v"
          MAC_STORE_APP_CERT:       ${{ secrets.MACAPP_CERT }} # Base64 encoded Mac App Distribution certificate
          MAC_STORE_APP_CERT_PWD:   ${{ secrets.MACAPP_CERT_PWD }}
          MAC_STORE_APP_CERT_ID:    ${{ secrets.MACAPP_CERT_ID }}
          MAC_STORE_INST_CERT:      ${{ secrets.MACAPP_INST_CERT }} # Base64 encoded Mac Installer Distribution certificate
          MAC_STORE_INST_CERT_PWD:  ${{ secrets.MACAPP_INST_CERT_PWD }}
          MAC_STORE_INST_CERT_ID:   ${{ secrets.MACAPP_INST_CERT_ID }}

Expected behavior

Certificate names in Xcode and autobuild process match.

Documentation

          ## Creating certificates
          #  Generate the certificates from Xcode. You can Manage Certificates in Apple Accounts settings or the Apple Developer account page.
          #  In Xcode Settings: Right click on Developer ID Application, Mac App Distribution (does not exist, maybe also developer id application??) and Mac Installer Distribution certificates.
          #  Select "Export Certificate"
          #  Set a secure password.
          #  For every certificate, export it as base64 encoded string with `base64 -i certificate.p12`
          #  Set the certificates based on the variables below

[pljones]

See also jamulussoftware/jamuluswebsite#1028

Should these two be merged? Is there a dependency between the two?

[ann0see]

No. This one is just for the macOS distributor. Which certificates to use and where to upload them.

[pljones]

This one is just for the macOS distributor.

Can autobuild not do it for a release?

[ann0see]

No. I don't think so and I'd consider this unsafe. The certificates must be created on macOS once per year.

Autobuild could upload binaries to AppStore Connect though.

[pljones]

Ah right, my misunderstanding of the whole macOS publishing mess...