[Spring] Adds feature useOptional (#5968)

* Adds Valid annotation for request body (#4847)

If useBeanValidation is active, this change will add Valid annotation to ReqeustBody

* Adds generated samples for bean vaildation in spring boot (#4847)

* Adds feature option (#3819)

When you enable the feature useOptional the JavaSpring generator will use type Optional for non required parameters.

* Adds generated sample for #3819

* Adds generated sample for #3819

* Reverts commit for bean validation

* Adds generated sample for #3819

* Reverts commit for bean validation

* Fix alignment

* update spring samples

* update pom.xml to include spring use optional samples

* update artifactId to "spring-boot-beanvalidation"

* rpelace tab with 4-space

* check mvn task result

samples/server/petstore/springboot-delegate/src/main/java/io/swagger/model/FormatTest.java

@@ -220,7 +220,7 @@ public class FormatTest   {
   @ApiModelProperty(required = true, value = "")
   @NotNull
 
-
+ @Pattern(regexp="^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$")
   public byte[] getByte() {
     return _byte;
   }