Document OkHttp callback for Android

Fixes getsentry#3630

src/platforms/android/configuration/integrations/okhttp.mdx

@@ -110,3 +110,61 @@ Learn more about manually capturing an error or message, in our <PlatformLink to
 </Note>
 
 To view and resolve the recorded message, log into [sentry.io](https://sentry.io) and open your project. Clicking on the error's title will open a page where you can see detailed information and mark it as resolved.
+
+## Customize recorded Span
+
+Captured Span can be customized or dropped with a `BeforeSpanCallback`:
+
+```kotlin
+import io.sentry.ISpan
+import io.sentry.android.okhttp.SentryOkHttpInterceptor
+import okhttp3.Request
+import okhttp3.Response
+
+class CustomBeforeSpanCallback : SentryOkHttpInterceptor.BeforeSpanCallback {
+  override fun execute(span: ISpan, request: Request, response: Response?): ISpan? {
+    return if (request.url.toUri().toString().contains("/admin")) {
+      null
+    } else {
+      span
+    }
+  }
+}
+```
+
+```java
+import io.sentry.ISpan;
+import io.sentry.android.okhttp.SentryOkHttpInterceptor;
+import okhttp3.Request;
+import okhttp3.Response;
+
+class CustomBeforeSpanCallback implements SentryOkHttpInterceptor.BeforeSpanCallback {
+  public ISpan execute(ISpan span, Request request, Response response) {
+    if (request.getUrl().toUri().toString().contains("/admin")) {
+      return null;
+    } else {
+      return span;
+    }
+  }
+}
+```
+
+The callback instance must be set on the `SentryOkHttpInterceptor` once you create your `OkHttpClient` instance.
+
+```kotlin
+import okhttp3.OkHttpClient
+import io.sentry.android.okhttp.SentryOkHttpInterceptor
+
+private val client = OkHttpClient.Builder()
+  .addInterceptor(SentryOkHttpInterceptor(CustomBeforeSpanCallback()))
+  .build()
+```
+
+```java
+import okhttp3.OkHttpClient;
+import io.sentry.android.okhttp.SentryOkHttpInterceptor;
+
+private final OkHttpClient client = new OkHttpClient.Builder()
+  .addInterceptor(new SentryOkHttpInterceptor(new CustomBeforeSpanCallback()))
+  .build();
+```