feat: Add creds for GitHub auth, add "none" auth to publisher (#276)

## Motivation and Context

- Adds credentials for the new MCP Registry Login GitHub Apps (local,
staging, prod)
- Adds support for "none" auth to publisher

## How Has This Been Tested?

- Tested publisher workflows locally
- Unit and integration tests passing

## Breaking Changes

None

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed

---

Merging based on Tadas's approval review, and only making minor docs changes on top of that.

tools/publisher/main.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/modelcontextprotocol/registry/tools/publisher/auth"
 	"github.com/modelcontextprotocol/registry/tools/publisher/auth/github"
+	"github.com/modelcontextprotocol/registry/tools/publisher/auth/none"
 )
 
 // Server structure types for JSON generation
@@ -103,8 +104,8 @@ func publishCommand() error {
 	publishFlags.StringVar(&registryURL, "registry-url", "", "URL of the registry (required)")
 	publishFlags.StringVar(&mcpFilePath, "mcp-file", "", "path to the MCP file (required)")
 	publishFlags.BoolVar(&forceLogin, "login", false, "force a new login even if a token exists")
-	publishFlags.StringVar(&authMethod, "auth-method", "github-oauth",
-		"authentication method to use (default: github-oauth)")
+	publishFlags.StringVar(&authMethod, "auth-method", "github",
+		"authentication method (github for authenticated, none for anonymous) (default: github)")
 
 	// Set custom usage function
 	publishFlags.Usage = func() {
@@ -116,7 +117,7 @@ func publishCommand() error {
 		fmt.Fprint(os.Stdout, "  --registry-url string    URL of the registry (required)\n")
 		fmt.Fprint(os.Stdout, "  --mcp-file string        path to the MCP file (required)\n")
 		fmt.Fprint(os.Stdout, "  --login                  force a new login even if a token exists\n")
-		fmt.Fprint(os.Stdout, "  --auth-method string     authentication method to use (default: github-oauth)\n")
+		fmt.Fprint(os.Stdout, "  --auth-method string     authentication method (github for authenticated, none for anonymous) (default: github)\n")
 	}
 
 	if err := publishFlags.Parse(os.Args[2:]); err != nil {
@@ -136,9 +137,12 @@ func publishCommand() error {
 
 	var authProvider auth.Provider // Determine the authentication method
 	switch authMethod {
-	case "github-oauth":
+	case "github":
 		log.Println("Using GitHub OAuth for authentication")
 		authProvider = github.NewOAuthProvider(forceLogin, registryURL)
+	case "none":
+		log.Println("Using anonymous authentication")
+		authProvider = none.NewProvider(registryURL)
 	default:
 		return fmt.Errorf("unsupported authentication method: %s", authMethod)
 	}