Some very minor refinements + doc

We usually try to avoid lambdas in runtime code as there is a small
price to pay.
In this case, they are easily avoidable.

Author: gsmet

docs/modules/ROOT/pages/developer-reference.adoc

@@ -370,6 +370,25 @@ You can use the constants present in `io.quarkiverse.githubapp.Credentials` for
 That is all you need to do:
 Quarkus GitHub App will then automatically use the values provided by the `CredentialsProvider` for the private key and the webhook secret.
 
+== Customizing the GitHub clients
+
+You can customize the GitHub clients initialized by Quarkus GitHub App
+by creating a CDI bean implementing `io.quarkiverse.githubapp.GitHubCustomizer`.
+
+For instance:
+
+[source,java]
+----
+@Singleton
+public class MyGitHubCustomizer implements GitHubCustomizer {
+
+    @Override
+    public void customize(GitHubBuilder builder) {
+       // call methods of the builder
+    }
+}
+----
+
 == Architecture Overview
 
 image::architecture.png[Architecture]

runtime/src/main/java/io/quarkiverse/githubapp/GitHubCustomizer.java

@@ -2,20 +2,21 @@
 
 import org.kohsuke.github.GitHubBuilder;
 
-import io.quarkiverse.githubapp.runtime.config.CheckedConfigProvider;
-
 /**
- * Seam for customizing the {@link GitHubBuilder} used to create the {@link org.kohsuke.github.GitHub} instance.
+ * Provide a CDI bean implementing this interface to customize {@link GitHubBuilder} used to create the
+ * {@link org.kohsuke.github.GitHub} instances.
  */
 public interface GitHubCustomizer {
 
     /**
-     * Customize the {@link GitHubBuilder} with various options for runtime.
+     * Customize the {@link GitHubBuilder} with various options.
      * <p>
      * Note that customizations that use {@link GitHubBuilder#withAppInstallationToken(String)} and
      * {@link GitHubBuilder#withEndpoint(String)} are eventually overridden by the
      * {@link io.quarkiverse.githubapp.runtime.github.GitHubService}. Installation tokens are created and cached by the service.
-     * To specify a custom endpoint, prefer the {@link CheckedConfigProvider#restApiEndpoint()}
+     * <p>
+     * To specify a custom endpoint, use configuration properties {@code quarkus.github-app.instance-endpoint} or
+     * {@code quarkus.github-app.rest-api-endpoint}.
      *
      * @param builder to customize
      */

runtime/src/main/java/io/quarkiverse/githubapp/runtime/github/GitHubService.java

@@ -35,6 +35,12 @@ public class GitHubService implements GitHubClientProvider {
 
     private static final String AUTHORIZATION_HEADER = "Authorization";
     private static final String AUTHORIZATION_HEADER_BEARER = "Bearer %s";
+    private static final GitHubCustomizer NOOP_GITHUB_CUSTOMIZER = new GitHubCustomizer() {
+
+        @Override
+        public void customize(GitHubBuilder builder) {
+        }
+    };
 
     private final CheckedConfigProvider checkedConfigProvider;
 
@@ -81,8 +87,7 @@ public long expireAfterRead(Long installationId, CachedInstallationToken cachedI
         this.gitHubConnector = new HttpClientGitHubConnector(
                 HttpClient.newBuilder().version(Version.HTTP_1_1).followRedirects(HttpClient.Redirect.NEVER).build());
         // if the customizer is not resolvable, we use a no-op customizer
-        githubCustomizer = gitHubCustomizer.isResolvable() ? gitHubCustomizer.get() : builder -> {
-        };
+        githubCustomizer = gitHubCustomizer.isResolvable() ? gitHubCustomizer.get() : NOOP_GITHUB_CUSTOMIZER;
     }
 
     @Override