Ensure configuration can be serialized

Closes gh-506

initializr-generator/src/main/java/io/spring/initializr/metadata/Dependency.java

@@ -425,6 +425,7 @@ public class Dependency extends MetadataElement implements Describable {
 		 */
 		private String version;
 
+		@JsonIgnore
 		private VersionRange range;
 
 		public String getGroupId() {

initializr-generator/src/main/java/io/spring/initializr/util/VersionProperty.java

@@ -20,6 +20,8 @@ import java.io.Serializable;
 import java.util.Arrays;
 import java.util.List;
 
+import com.fasterxml.jackson.annotation.JsonValue;
+
 import org.springframework.util.StringUtils;
 
 /**
@@ -55,6 +57,7 @@ public class VersionProperty implements Serializable, Comparable<VersionProperty
 		return sb.toString();
 	}
 
+	@JsonValue
 	public String toStandardFormat() {
 		return this.property;
 	}

initializr-generator/src/test/resources/application-test-default.yml

@@ -8,6 +8,7 @@ initializr:
       my-api-bom:
         groupId: org.acme
         artifactId: my-api-bom
+        versionProperty: my-api.version
         additionalBoms: ['my-api-dependencies-bom']
         mappings:
           - versionRange: "[1.0.0.RELEASE,1.1.6.RELEASE)"