fix proxy mode failing for GH private packages (#137)

* fix proxy mode failing for GH private packages

* skip analysis for private packages for proxy mode

* introduce npmRegistryConfig and support for handling multiple parsers in future

* refactor name and unexport npm config functions

* rm unused function

* rename & unexport npmRegistryURLParser

* add e2e for malicious pkg blocked using proxy mode

proxy/interceptors/npm_registry_config.go

@@ -0,0 +1,32 @@
+package interceptors
+
+import "strings"
+
+// npmRegistryConfig defines configuration for npm registry endpoints
+type npmRegistryConfig struct {
+	// Hostname
+	Host string
+
+	// Whether this registry is supported for malware analysis
+	SupportedForAnalysis bool
+
+	// Parser for the registry
+	RegistryParser npmRegistryURLParser
+}
+
+// getNpmRegistryConfigForHostname returns the configuration for a hostname (with subdomain matching)
+func getNpmRegistryConfigForHostname(hostname string) *npmRegistryConfig {
+	// Check exact match first
+	if config, exists := npmRegistryDomains[hostname]; exists {
+		return config
+	}
+
+	// Check subdomain match: hostname could be "cdn.registry.npmjs.org" matching "registry.npmjs.org"
+	for endpoint, config := range npmRegistryDomains {
+		if strings.HasSuffix(hostname, "."+endpoint) {
+			return config
+		}
+	}
+
+	return nil
+}