Clarify what makes URL browser incompatible (#3019)

Author: dagnir

services/s3/src/main/java/software/amazon/awssdk/services/s3/presigner/S3Presigner.java

@@ -61,7 +61,7 @@
  * requiring access to Alice's credentials.
  * <p/>
  *
- * <b>Signature Duration</b>
+ * <h2>Signature Duration</h2>
  * <p/>
  *
  * Pre-signed requests are only valid for a finite period of time, referred to as the signature duration. This signature
@@ -70,7 +70,7 @@
  * duration has passed will result in an access denied response from the service.
  * <p/>
  *
- * <b>Example Usage</b>
+ * <h3>Example Usage</h3>
  * <p/>
  *
  * <pre>
@@ -109,7 +109,7 @@
  * </pre>
  * <p/>
  *
- * <b>Browser Compatibility</b>
+ * <h2>Browser Compatibility</h2>
  * <p/>
  *
  * Some pre-signed requests can be executed by a web browser. These "browser compatible" pre-signed requests
@@ -123,7 +123,24 @@
  * being browser-compatible.
  * <p />
  *
- * <b>Executing a Pre-Signed Request from Java code</b>
+ * <h3>Configurations that affect browser compatibility</h3>
+ * <h4>Enabling Checking Validation</h4>
+ * If checksum validations are enabled, the presigned URL will no longer be browser compatible because it adds a signed header
+ * that must be included in the HTTP request.
+ *
+ * Checksum validation is disabled in the presigner by default, but when using a custom {@link S3Configuration} when enabling
+ * features like path style access or accelerate mode, it must be explicitly disabled:
+ *
+ * <pre>
+ *         S3Presigner presigner = S3Presigner.builder()
+ *                                            .serviceConfiguration(S3Configuration.builder()
+ *                                                                                 .checksumValidationEnabled(false)
+ *                                                                                 .build())
+ *                                            .build();
+ * </pre>
+ *
+ *
+ * <h2>Executing a Pre-Signed Request from Java code</h2>
  * <p />
  *
  * Browser-compatible requests (see above) can be executed using a web browser. All pre-signed requests can be executed