Add optional links to a dependency

See gh-163

initializr-web/src/main/groovy/io/spring/initializr/web/mapper/DependencyMetadataV21JsonMapper.groovy

@@ -57,6 +57,9 @@ class DependencyMetadataV21JsonMapper implements DependencyMetadataJsonMapper {
 		if (dep.repository) {
 			result.repository = dep.repository
 		}
+		if (dep.links) {
+			result.links = dep.links
+		}
 		result
 	}
 

initializr-web/src/main/groovy/io/spring/initializr/web/mapper/InitializrMetadataV21JsonMapper.groovy

@@ -52,6 +52,9 @@ class InitializrMetadataV21JsonMapper extends InitializrMetadataV2JsonMapper {
 		if (dependency.versionRange) {
 			content['versionRange'] = dependency.versionRange
 		}
+		if (dependency.links) {
+			content.links = dependency.links
+		}
 		content
 	}
 

initializr-web/src/main/groovy/io/spring/initializr/web/ui/UiController.groovy

@@ -82,6 +82,10 @@ class UiController {
 		if (d.description) {
 			result.description = d.description
 		}
+		if (d.links) {
+			result.url = d.links[0].url
+			result.links = d.links
+		}
 		if (d.weight) {
 			result.weight = d.weight
 		}