[Documentation] Road to macOS Catalina

[sieren]

We want to support MacOS Catalina with Synth One.
The MVP-Goal is to have a first running version of Synth One available in the App Store.
Further goals could be adding AUv3 support.

This document is supposed to track progress towards that goal.

Current state
I managed to get a build of Synth One running on Catalina, that produces audio output.

Unfortunately this is far from releasable. The biggest current obstacles are:

• Cocoapods does not support iOSMac targets (Catalyst)
• We use a lot of third-party frameworks that are closed source and not compiled for iOSMac.
• There are a lot of UIKit related crashes that warrant further investigation

Current steps

• Remove ChimpKit from S1 (Dated framework, no update in 5 years): Replace ChimpKit SDK Dependency #118

• Remove EZAudio OpenGL dependencies from AudioKit: Remove EZAudioPlotGL from all Platforms AudioKit#1912 & Cleanup: Remove EZAudioPlotGL from other Platform Projects AudioKit#1913

• Remove AudioBus/IAA from Mac targets: [Cataylst] Make IAA/AB Platform dependent #120

• Figure out what to do with OneSignal and MS AppCenter dependencies: [Cataylst] Refactor Platform Services/Dependencies #121

• Figure out what to do with Cocoapods support

• Need support for LSSupportsOpeningDocumentsInPlace across platforms

• Resolve all the other issues (S1 crashes on any other screen than the home-screen, presumably due to some Storyboard issues)

How to build it currently
Currently building for Catalina requires the following steps:

• Remove all Pods except for "Disk" from Podfile
• Drop in iOS Project for AudioKit
• Set checkbox for macOS
• Fix missing entitlements and code-sign issues (@analogcode needs to add those at some point)
• Build for Catalina (iOS builds will not work due to the missing Pods)