Make services optional.

Also update the doc.

doc/configuration.md

@@ -33,10 +33,7 @@ one-element array.
 ### `hosts`
 
 `hosts` is a list of hostname bindings. These map possibly-wildcarded hostnames
-to certificate-key pairs to use to authenticate an endpoint as those hosts. This
-section is only required if at least one endpoint is to respond to
-host-authenticated protocols (which is of course probably going to be most of
-the time).
+to certificate-key pairs to use to authenticate an endpoint as those hosts.
 
 ```js
 const hosts = [
@@ -60,6 +57,10 @@ the underlying certificates, where a `*` denotes exactly one subdomain. And, to
 be clear, the hostname `*` will match _any_ hostname at all, with any number of
 subdomains.
 
+This section is only required if at least one endpoint is to respond to
+host-authenticated protocols (which is nearly always, at least in standalone
+uses).
+
 **Note:** If you want to keep the text of the keys and certificates out of the
 main configuration file, then the thing to do is just use the standard Node `fs`
 package to read the contents.
@@ -86,6 +87,8 @@ const services = [
   // ... more ...
 ```
 
+This section is only required if there are any services being defined at all.
+
 ### `applications`
 
 `applications` is a list of applications to be used, with each element naming

src/app-config/export/WarehouseConfig.js

@@ -20,7 +20,8 @@ import { ServiceConfig } from '#x/ServiceConfig';
  * * `{object|object[]} hosts` -- Optional host / certificate configuration.
  *   Required only if any endpoints are configured to listen for secure
  *   connections.
- * * `{object|object[]} services` -- System service configuration.
+ * * `{object|object[]} services` -- Optional system service configuration.
+ *   If not present, no services are configured.
  */
 export class WarehouseConfig extends BaseConfig {
   /** @type {ApplicationConfig[]} Application configuration objects. */
@@ -50,7 +51,7 @@ export class WarehouseConfig extends BaseConfig {
       applications,
       endpoints,
       hosts = [],
-      services
+      services = []
     } = config;
 
     this.#applications = ApplicationConfig.parseArray(applications, configClassMapper);