docs: update validation documentation

docs/utilities/validation.md

@@ -83,7 +83,9 @@ You can validate inbound and outbound events using `@Validation` annotation.
 
 You can also use the `Validator#validate()` methods, if you want more control over the validation process such as handling a validation error.
 
-We support JSON schema version 4, 6, 7 and 201909 (from [jmespath-jackson library](https://github.com/burtcorp/jmespath-java)).
+We support JSON schema version 4, 6, 7, 2019-09 and 2020-12 using the [NetworkNT JSON Schema Validator](https://github.com/networknt/json-schema-validator). ([Compatibility with JSON Schema versions](https://github.com/networknt/json-schema-validator/blob/master/doc/compatibility.md)).
+
+The validator is configured to enable format assertions by default even for 2019-09 and 2020-12.
 
 ### Validation annotation
 
@@ -228,7 +230,8 @@ and [function](https://jmespath.org/tutorial.html#functions) expressions, where
 
 
 ## Change the schema version
-By default, powertools-validation is configured with [V7](https://json-schema.org/draft-07/json-schema-release-notes.html).
+By default, powertools-validation is configured to use [V7](https://json-schema.org/draft-07/json-schema-release-notes.html) as the default dialect if [`$schema`](https://json-schema.org/understanding-json-schema/reference/schema#schema) is not explicitly specified within the schema. If [`$schema`](https://json-schema.org/understanding-json-schema/reference/schema#schema) is explicitly specified within the schema, the validator will use the specified dialect.
+
 You can use the `ValidationConfig` to change that behaviour.
 
 === "Handler with custom schema version"

powertools-validation/src/main/java/software/amazon/lambda/powertools/validation/ValidationConfig.java

@@ -47,9 +47,15 @@ public SpecVersion.VersionFlag getSchemaVersion() {
     }
 
     /**
-     * Set the version of the json schema specifications (default is V7)
+     * Set the version of the json schema specifications to use if $schema is not
+     * explicitly specified within the schema (default is V7). If $schema is
+     * explicitly specified within the schema is explicitly specified within the
+     * schema, the validator will use the specified dialect.
      *
      * @param version May be V4, V6, V7, V201909 or V202012
+     * @see <a href=
+     *      "https://json-schema.org/understanding-json-schema/reference/schema#declaring-a-dialect">Declaring
+     *      a Dialect</a>
      */
     public void setSchemaVersion(SpecVersion.VersionFlag version) {
         if (version != jsonSchemaVersion) {