feat: kadabra, the app auto-updater (!268)

coop-cloud/organising#236

Autoupdater `kadabra` is ready for testing.
It should run on the server, check for available minor/patch updates and automatically upgrade the apps.

Co-authored-by: Moritz <moritz.m@local-it.org>
Reviewed-on: coop-cloud/abra#268

cmd/kadabra/main.go

@@ -0,0 +1,23 @@
+// Package main provides the command-line entrypoint.
+package main
+
+import (
+	"coopcloud.tech/abra/cli/updater"
+)
+
+// Version is the current version of Abra
+var Version string
+
+// Commit is the current git commit of Abra
+var Commit string
+
+func main() {
+	if Version == "" {
+		Version = "dev"
+	}
+	if Commit == "" {
+		Commit = "       "
+	}
+
+	updater.RunApp(Version, Commit)
+}