Add remove json attributes filter (#2742)

* Add RemoveJsonAttributesFilterFactory
Takes a collection of attribute names to search for to remove from a JSON response, an optional last parameter from the list can be a boolean to remove the attributes just at root level or recursively

* Add docs for RemoveJsonAttributes filter

* Extract a single instance of Json mapper

* Overload boolean parameter to avoid parsing a string

docs/src/main/asciidoc/spring-cloud-gateway.adoc

@@ -1118,6 +1118,51 @@ spring:
 
 This will send a status 302 with a `Location:https://acme.org` header to perform a redirect.
 
+=== `RemoveJsonAttributesResponseBody` `GatewayFilter` Factory
+
+The `RemoveJsonAttributesResponseBody` `GatewayFilter` factory takes a collection of `attribute names` to search for, an optional last parameter from the list can be a boolean to remove the attributes just at root level (that's the default value if not present at the end of the parameter configuration, `false`) or recursively (`true`).
+It provides a convenient method to apply a transformation to JSON body content by deleting attributes from it.
+
+The following example configures an `RemoveJsonAttributesResponseBody` `GatewayFilter`:
+
+.application.yml
+====
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: removejsonattributes_route
+        uri: https://example.org
+        filters:
+        - RemoveJsonAttributesResponseBody=id,color
+----
+====
+
+This removes attributes "id" and "color" from the JSON content body at root level.
+
+The following example configures an `RemoveJsonAttributesResponseBody` `GatewayFilter` that uses the optional last parameter:
+
+.application.yml
+====
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: removejsonattributes_recursively_route
+        uri: https://example.org
+        predicates:
+        - Path=/red/{segment}
+        filters:
+        - RemoveJsonAttributesResponseBody=id,color,true
+----
+====
+
+This removes attributes "id" and "color" from the JSON content body at any level.
+
 === The `RemoveRequestHeader` GatewayFilter Factory
 
 The `RemoveRequestHeader` `GatewayFilter` factory takes a `name` parameter.