Deprecate mackup formula due to potential for silent data loss

The `mackup` program works by moving config files to an off-disk backup location (usually a cloud storage provider like iCloud or Dropbox, etc.) and then replacing the original file with a symlink to the backed up version. The intended use is to make sure program configuration settings and preferences can be restored if you need to replace computers, factory reset, etc.

As documented [here](lra/mackup#2035), [here](lra/mackup#1924), [here](lra/mackup#1969 (reply in thread)), `mackup backup` no longer works on MacOS Sonoma (possibly due to [security changes](lra/mackup#1924 (comment)) in the app sandbox in Sonoma) and running the command will result in the loss of all preference files. Users who backup to a storage provider that has versioning or backup snapshots may be able to restore preferences to an older version. For users backing up to other storage providers that do not have this feature, such as iCloud, the command results in total data loss. This issue has been known to the developer for over a year but there is no fix, no mention of the issue in the project README, no warning when running the command, and no indication in the program output that the backup process may not have completed properly - neither in the dry-run mode nor in live mode.

Formula/m/mackup.rb

@@ -8,6 +8,11 @@ class Mackup < Formula
   license "GPL-3.0-or-later"
   head "https://github.com/lra/mackup.git", branch: "master"
 
+  # see discussions in https://github.com/lra/mackup/issues/2035,
+  # https://github.com/lra/mackup/issues/1924,
+  # and https://github.com/lra/mackup/discussions/1969#discussioncomment-8485995
+  deprecate! date: "2024-08-19", because: "Potential data loss on MacOS Sonoma"
+
   bottle do
     sha256 cellar: :any_skip_relocation, arm64_sonoma:   "dac4b2e6a5dbb4b99eeb476ca7a80d7b313dab3f733474ab24c6ad02bee7637e"
     sha256 cellar: :any_skip_relocation, arm64_ventura:  "dac4b2e6a5dbb4b99eeb476ca7a80d7b313dab3f733474ab24c6ad02bee7637e"