Implement --deploy-token-auth in GitLab bootstrapping

This change set implements support for the `--deploy-token-auth` option
in the `flux bootstrap gitlab` command.

That option will reconcile a GitLab Project Deploy Token to use for the
authentication of the GitLab git repository.
A GitLab Project Deploy Token can be used the same way as a Personal
Access Token which is already supported via `--token-auth`.
The difference with the GitLab Project Deploy Token is that the token is
managed (created, updated, deleted) by Flux and not provided by the
user.

This change is transparent to the source-controller.

A prerequisite for this change is the
`fluxcd/go-git-providers` change here:

* https://github.com/fluxcd/go-git-providers/pull/191

See related discussion here: https://github.com/fluxcd/flux2/discussions/3595
GitLab Issue here: https://gitlab.com/gitlab-org/gitlab/-/issues/392605

Signed-off-by: Timo Furrer <tuxtimo@gmail.com>

cmd/flux/bootstrap_gitlab.go

@@ -65,7 +65,11 @@ the bootstrap command will perform an upgrade if needed.`,
   flux bootstrap gitlab --owner=<group> --repository=<repository name> --hostname=<domain> --token-auth
 
   # Run bootstrap for a an existing repository with a branch named main
-  flux bootstrap gitlab --owner=<organization> --repository=<repository name> --branch=main --token-auth`,
+  flux bootstrap gitlab --owner=<organization> --repository=<repository name> --branch=main --token-auth
+
+  # Run bootstrap for a private repository using Deploy Token authentication
+  flux bootstrap gitlab --owner=<group> --repository=<repository name> --deploy-token-auth
+  `,
 	RunE: bootstrapGitLabCmdRun,
 }
 
@@ -77,16 +81,17 @@ const (
 )
 
 type gitlabFlags struct {
-	owner        string
-	repository   string
-	interval     time.Duration
-	personal     bool
-	private      bool
-	hostname     string
-	path         flags.SafeRelativePath
-	teams        []string
-	readWriteKey bool
-	reconcile    bool
+	owner           string
+	repository      string
+	interval        time.Duration
+	personal        bool
+	private         bool
+	hostname        string
+	path            flags.SafeRelativePath
+	teams           []string
+	readWriteKey    bool
+	reconcile       bool
+	deployTokenAuth bool
 }
 
 var gitlabArgs gitlabFlags
@@ -102,6 +107,7 @@ func init() {
 	bootstrapGitLabCmd.Flags().Var(&gitlabArgs.path, "path", "path relative to the repository root, when specified the cluster sync will be scoped to this path")
 	bootstrapGitLabCmd.Flags().BoolVar(&gitlabArgs.readWriteKey, "read-write-key", false, "if true, the deploy key is configured with read/write permissions")
 	bootstrapGitLabCmd.Flags().BoolVar(&gitlabArgs.reconcile, "reconcile", false, "if true, the configured options are also reconciled if the repository already exists")
+	bootstrapGitLabCmd.Flags().BoolVar(&gitlabArgs.deployTokenAuth, "deploy-token-auth", false, "when enabled, a Project Deploy Token is generated and will be used instead of the SSH deploy token")
 
 	bootstrapCmd.AddCommand(bootstrapGitLabCmd)
 }
@@ -123,6 +129,10 @@ func bootstrapGitLabCmdRun(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
+	if bootstrapArgs.tokenAuth && gitlabArgs.deployTokenAuth {
+		return fmt.Errorf("--token-auth and --deploy-token-auth cannot be set both.")
+	}
+
 	if err := bootstrapValidate(); err != nil {
 		return err
 	}
@@ -225,6 +235,9 @@ func bootstrapGitLabCmdRun(cmd *cobra.Command, args []string) error {
 		secretOpts.Username = "git"
 		secretOpts.Password = glToken
 		secretOpts.CAFile = caBundle
+	} else if gitlabArgs.deployTokenAuth {
+		// the actual deploy token will be reconciled later
+		secretOpts.CAFile = caBundle
 	} else {
 		keypair, err := sourcesecret.LoadKeyPairFromPath(bootstrapArgs.privateKeyFile, gitArgs.password)
 		if err != nil {
@@ -274,9 +287,12 @@ func bootstrapGitLabCmdRun(cmd *cobra.Command, args []string) error {
 	if bootstrapArgs.sshHostname != "" {
 		bootstrapOpts = append(bootstrapOpts, bootstrap.WithSSHHostname(bootstrapArgs.sshHostname))
 	}
-	if bootstrapArgs.tokenAuth {
+	if bootstrapArgs.tokenAuth || gitlabArgs.deployTokenAuth {
 		bootstrapOpts = append(bootstrapOpts, bootstrap.WithSyncTransportType("https"))
 	}
+	if gitlabArgs.deployTokenAuth {
+		bootstrapOpts = append(bootstrapOpts, bootstrap.WithDeployTokenAuth())
+	}
 	if !gitlabArgs.private {
 		bootstrapOpts = append(bootstrapOpts, bootstrap.WithProviderRepositoryConfig("", "", "public"))
 	}