Adding --join-method flag to teleport configure command

[WilliamLoy]

A customer requested the --join-method flag be made available as an option when using the teleport configure command.

I didn't see a technical reason as to why this flag wasn't already available in the command so I've added it to this PR.

Changelog: Added a --join-method flag to the teleport configure command

[WilliamLoy]

@rosstimothy I'd appreciate a review if you have the time.

[rosstimothy]

This looks good, but I think we can future proof things a bit if we don't hardcode the join methods and instead leverage types.JoinMethods.

What do you think about the following change?

diff --git a/go.mod b/go.mod
index 89090133d3..eab9cbd704 100644
--- a/go.mod
+++ b/go.mod
@@ -592,3 +592,5 @@ replace (
 	github.com/redis/go-redis/v9 => github.com/gravitational/redis/v9 v9.6.1-teleport.1
 	github.com/vulcand/predicate => github.com/gravitational/predicate v1.3.2
 )
+
+exclude google.golang.org/grpc/stats/opentelemetry v0.0.0-20241028142157-ada6787961b3
diff --git a/tool/teleport/common/teleport.go b/tool/teleport/common/teleport.go
index 4ab0ad433e..699da3468d 100644
--- a/tool/teleport/common/teleport.go
+++ b/tool/teleport/common/teleport.go
@@ -395,6 +395,11 @@ func Run(options Options) (app *kingpin.Application, executedCommand string, con
 	scpc.Flag("local-addr", "local address which accepted the request").StringVar(&scpFlags.LocalAddr)
 	scpc.Arg("target", "").StringsVar(&scpFlags.Target)
 
+	joinMethods := make([]string, 0, len(types.JoinMethods))
+	for _, m := range types.JoinMethods {
+		joinMethods = append(joinMethods, string(m))
+	}
+
 	// dump flags
 	dump.Flag("cluster-name",
 		"Unique cluster name, e.g. example.com.").StringVar(&dumpFlags.ClusterName)
@@ -412,7 +417,7 @@ func Run(options Options) (app *kingpin.Application, executedCommand string, con
 	dump.Flag("key-file", "Path to a TLS key file for the proxy.").ExistingFileVar(&dumpFlags.KeyFile)
 	dump.Flag("data-dir", "Path to a directory where Teleport keep its data.").Default(defaults.DataDir).StringVar(&dumpFlags.DataDir)
 	dump.Flag("token", "Invitation token or path to file with token value to register with an auth server.").StringVar(&dumpFlags.AuthToken)
-	dump.Flag("join-method", "Method to use to join the cluster (token, iam, ec2, kubernetes, azure, gcp, oracle, github, circleci, gitlab, tpm)").Default("token").EnumVar(&dumpFlags.JoinMethod, "token", "iam", "ec2", "kubernetes", "azure", "gcp", "oracle", "github", "circleci", "tpm")
+	dump.Flag("join-method", fmt.Sprintf("Method to use to join the cluster (%s)", strings.Join(joinMethods, ", "))).Default("token").EnumVar(&dumpFlags.JoinMethod, joinMethods...)
 	dump.Flag("roles", "Comma-separated list of roles to create config with.").StringVar(&dumpFlags.Roles)
 	dump.Flag("auth-server", "Address of the auth server.").StringVar(&dumpFlags.AuthServer)
 	dump.Flag("proxy", "Address of the proxy.").StringVar(&dumpFlags.ProxyAddress)
@@ -430,6 +435,7 @@ func Run(options Options) (app *kingpin.Application, executedCommand string, con
 	dumpNodeConfigure.Flag("output",
 		`Write to stdout with "--output=stdout", default config file with "--output=file" or custom path with --output=file:///path`).Short('o').Default(
 		teleport.SchemeStdout).StringVar(&dumpFlags.output)
+
 	dumpNodeConfigure.Flag("version", "Teleport configuration version.").Default(defaults.TeleportConfigVersionV3).StringVar(&dumpFlags.Version)
 	dumpNodeConfigure.Flag("public-addr", "The hostport that the node advertises for the SSH endpoint.").StringVar(&dumpFlags.PublicAddr)
 	dumpNodeConfigure.Flag("data-dir", "Path to a directory where Teleport keep its data.").Default(defaults.DataDir).StringVar(&dumpFlags.DataDir)
@@ -438,7 +444,7 @@ func Run(options Options) (app *kingpin.Application, executedCommand string, con
 	dumpNodeConfigure.Flag("proxy", "Address of the proxy server.").StringVar(&dumpFlags.ProxyAddress)
 	dumpNodeConfigure.Flag("labels", "Comma-separated list of labels to add to newly created nodes ex) env=staging,cloud=aws.").StringVar(&dumpFlags.NodeLabels)
 	dumpNodeConfigure.Flag("ca-pin", "Comma-separated list of SKPI hashes for the CA used to verify the auth server.").StringVar(&dumpFlags.CAPin)
-	dumpNodeConfigure.Flag("join-method", "Method to use to join the cluster (token, iam, ec2, kubernetes, azure, gcp, oracle, github, circleci, gitlab, tpm)").Default("token").EnumVar(&dumpFlags.JoinMethod, "token", "iam", "ec2", "kubernetes", "azure", "gcp", "oracle", "github", "circleci", "tpm")
+	dumpNodeConfigure.Flag("join-method", fmt.Sprintf("Method to use to join the cluster (%s)", strings.Join(joinMethods, ", "))).Default("token").EnumVar(&dumpFlags.JoinMethod, joinMethods...)
 	dumpNodeConfigure.Flag("node-name", "Name for the Teleport node.").StringVar(&dumpFlags.NodeName)
 	dumpNodeConfigure.Flag("silent", "Suppress user hint message.").BoolVar(&dumpFlags.Silent)
 	dumpNodeConfigure.Flag("azure-client-id", "Sets the client ID of the managed identity to join with. Only applies to the 'azure' join method.").StringVar(&dumpFlags.AzureClientID)

[WilliamLoy]

@rosstimothy I incorporated your suggestion. Thank you.

[public-teleport-github-review-bot]

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