add logout command

Context: we'll want to give our customers the ability to clear out their
sessions and prune out any access tokens.

internal/cli/cli.go

@@ -229,6 +229,38 @@ func (c *cli) addTenant(ten tenant) error {
 	return nil
 }
 
+func (c *cli) removeTenant(ten string) error {
+	// init will fail here with a `no tenant found` error if we're logging
+	// in for the first time and that's expected.
+	_ = c.init()
+
+	// If we're dealing with an empty file, we'll need to initialize this
+	// map.
+	if c.config.Tenants == nil {
+		c.config.Tenants = map[string]tenant{}
+	}
+
+	// If the default tenant is being removed, we'll pick the first tenant
+	// that's not the one being removed, and make that the new default.
+	if c.config.DefaultTenant == ten {
+	Loop:
+		for t := range c.config.Tenants {
+			if t != ten {
+				c.config.DefaultTenant = t
+				break Loop
+			}
+		}
+	}
+
+	delete(c.config.Tenants, ten)
+
+	if err := c.persistConfig(); err != nil {
+		return fmt.Errorf("persisting config: %w", err)
+	}
+
+	return nil
+}
+
 func (c *cli) persistConfig() error {
 	dir := filepath.Dir(c.path)
 	if _, err := os.Stat(dir); os.IsNotExist(err) {

internal/cli/root.go

@@ -34,6 +34,12 @@ func Execute() {
 				return nil
 			}
 
+			// If the user is trying to logout, session information
+			// isn't important as well.
+			if cmd.Use == "logout" && cmd.Parent().Use == "auth0" {
+				return nil
+			}
+
 			// Selecting tenants shouldn't really trigger a login.
 			if cmd.Use == "use" && cmd.Parent().Use == "tenants" {
 				return nil
@@ -72,6 +78,7 @@ func Execute() {
 	rootCmd.AddCommand(testCmd(cli))
 	rootCmd.AddCommand(logsCmd(cli))
 	rootCmd.AddCommand(actionsCmd(cli))
+	rootCmd.AddCommand(logoutCmd(cli))
 
 	// keep completion at the bottom:
 	rootCmd.AddCommand(completionCmd(cli))