refactor to use app package instead of service

refactor app to be composable

internal/utils/shellcomp/completion.go

@@ -0,0 +1,10 @@
+package shellcomp
+
+import "github.com/spf13/cobra"
+
+// CompletionFunc returns a function that provides shell completion for the given options.
+func CompletionFunc(options []string) func(*cobra.Command, []string, string) ([]string, cobra.ShellCompDirective) {
+	return func(_ *cobra.Command, _ []string, _ string) ([]string, cobra.ShellCompDirective) {
+		return options, cobra.ShellCompDirectiveDefault
+	}
+}