feat: make the creation of new QuerySpec easier

Make the creation of new QuerySpec instances easier by using chained
Accessors. This make the feature not binary compatible, but given that
we're just returning QuerySpecs instead of void, everything should
compile, thus this is not a breaking change.

Closes #93

backend-core-model/src/main/java/com/flowingcode/backendcore/model/QuerySpec.java

@@ -26,10 +26,11 @@
 import java.util.Collection;
 import java.util.LinkedHashMap;
 import java.util.Map;
-import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.Setter;
+import lombok.experimental.Accessors;
 
+@Accessors(chain=true)
 public class QuerySpec {
 
 	public enum Order {
@@ -51,19 +52,22 @@ public enum Order {
 	@Getter
 	private final Collection<Constraint> constraints = new ArrayList<>();
 
-	public void addOrder(String property, Order order) {
+	public QuerySpec addOrder(String property, Order order) {
 		if (this.orders == null) {
 			this.orders = new LinkedHashMap<>();
 		}
 		this.orders.put(property, order);
+		return this;
 	}
 
-	public void addOrder(String property) {
+	public QuerySpec addOrder(String property) {
 		addOrder(property, Order.ASC);
+		return this;
 	}
 
-	public void addConstraint(Constraint constraint) {
+	public QuerySpec addConstraint(Constraint constraint) {
 		this.constraints.add(constraint);
+		return this;
 	}
 
 	@Override
@@ -107,18 +111,20 @@ public Integer getMaxResult() {
      * @return the same query instance
      * @throws IllegalArgumentException if the argument is negative
      */
-	public void setFirstResult(Integer firstResult) {
+	public QuerySpec setFirstResult(Integer firstResult) {
 	  if (firstResult!=null && firstResult<0) throw new IllegalArgumentException();
       this.firstResult = firstResult;
+      return this;
     }
 
     /**
      * Set the maximum number of results to retrieve.
      * @param maxResult  maximum number of results to retrieve (may be null)
      * @throws IllegalArgumentException if the argument is negative
      */
-	public void setMaxResult(Integer maxResult) {
+	public QuerySpec setMaxResult(Integer maxResult) {
 	  if (maxResult!=null && maxResult<0) throw new IllegalArgumentException();
       this.maxResult = maxResult;
+      return this;
     }
 }