Provide option to add appendix to commit messages

Using the `--commit-message-appendix` flag a string can be added to the
commit messages made by the bootstrapper process to for example skip CI
actions from executing using e.g. `[skip ci]`.

Signed-off-by: Hidde Beydals <hello@hidde.co>

cmd/flux/bootstrap_git.go

@@ -196,6 +196,7 @@ func bootstrapGitCmdRun(cmd *cobra.Command, args []string) error {
 		bootstrap.WithRepositoryURL(gitArgs.url),
 		bootstrap.WithBranch(bootstrapArgs.branch),
 		bootstrap.WithAuthor(bootstrapArgs.authorName, bootstrapArgs.authorEmail),
+		bootstrap.WithCommitMessageAppendix(bootstrapArgs.commitMessageAppendix),
 		bootstrap.WithKubeconfig(rootArgs.kubeconfig, rootArgs.kubecontext),
 		bootstrap.WithPostGenerateSecretFunc(promptPublicKey),
 		bootstrap.WithLogger(logger),