feat: support custom headers

cmd/root.go

@@ -68,6 +68,7 @@ func init() {
 	rootCmd.PersistentFlags().String("client-id", "", "Client ID. Sent to the Token Issuer during the Client Credentials flow")                            //nolint:lll
 	rootCmd.PersistentFlags().String("client-secret", "", "Client Secret. Sent to the Token Issuer during the Client Credentials flow")                    //nolint:lll
 	rootCmd.PersistentFlags().StringArray("api-scopes", []string{}, "API Scopes (repeat option for multiple values). Used in the Client Credentials flow") //nolint:lll
+	rootCmd.PersistentFlags().StringArray("custom-headers", []string{}, "Custom HTTP Headers (repeat option for multiple values)")                         //nolint:lll
 	rootCmd.PersistentFlags().Bool("debug", false, "Enable debug mode - can print more detailed information for debugging")
 
 	_ = rootCmd.Flags().MarkHidden("debug")

internal/cmdutils/get-client-config.go

@@ -44,6 +44,7 @@ func GetClientConfig(cmd *cobra.Command) fga.ClientConfig {
 	clientCredentialsClientID, _ := cmd.Flags().GetString("client-id")
 	clientCredentialsClientSecret, _ := cmd.Flags().GetString("client-secret")
 	clientCredentialsScopes, _ := cmd.Flags().GetStringArray("api-scopes")
+	customHeaders, _ := cmd.Flags().GetStringArray("custom-headers")
 	debug, _ := cmd.Flags().GetBool("debug")
 
 	return fga.ClientConfig{
@@ -56,6 +57,7 @@ func GetClientConfig(cmd *cobra.Command) fga.ClientConfig {
 		ClientID:             clientCredentialsClientID,
 		ClientSecret:         clientCredentialsClientSecret,
 		APIScopes:            clientCredentialsScopes,
+		CustomHeaders:        customHeaders,
 		Debug:                debug,
 	}
 }

internal/fga/fga.go

@@ -44,6 +44,7 @@ type ClientConfig struct {
 	APIScopes            []string `json:"api_scopes,omitempty"`
 	ClientID             string   `json:"client_id,omitempty"`
 	ClientSecret         string   `json:"client_secret,omitempty"` //nolint:gosec
+	CustomHeaders        []string `json:"custom_headers,omitempty"`
 	Debug                bool     `json:"debug,omitempty"`
 }
 
@@ -95,6 +96,20 @@ func (c ClientConfig) getClientConfig() *client.ClientConfiguration {
 			MaxRetry:    MaxSdkRetry,
 			MinWaitInMs: MinSdkWaitInMs,
 		},
-		Debug: c.Debug,
+		Debug:          c.Debug,
+		DefaultHeaders: c.getCustomHeaders(),
 	}
 }
+
+func (c ClientConfig) getCustomHeaders() map[string]string {
+	headers := map[string]string{}
+	for _, header := range c.CustomHeaders {
+		parts := strings.SplitN(header, ":", 2)
+		if len(parts) == 2 {
+			head := strings.TrimSpace(parts[0])
+			value := strings.TrimSpace(parts[1])
+			headers[head] = value
+		}
+	}
+	return headers
+}