add micronaut openapi spec generation

pom.xml

@@ -18,6 +18,7 @@
     <!-- If you are building with JDK 9 or higher, you can uncomment the lines below to set the release version -->
     <release.version>14</release.version>
     <micronaut.version>2.0.1</micronaut.version>
+    <micronautopenapi.version>2.0.0</micronautopenapi.version>
     <exec.mainClass>dev.amatos.restcountries.Application</exec.mainClass>
     <java.version>14</java.version>
   </properties>
@@ -105,6 +106,10 @@
       <artifactId>resteasy-client</artifactId>
       <version>4.5.7.Final</version>
     </dependency>
+    <dependency>
+      <groupId>io.swagger.core.v3</groupId>
+      <artifactId>swagger-annotations</artifactId>
+    </dependency>
   </dependencies>
 
   <build>
@@ -139,6 +144,11 @@
               <artifactId>micronaut-validation</artifactId>
               <version>${micronaut.version}</version>
             </path>
+            <path>
+              <groupId>io.micronaut.openapi</groupId>
+              <artifactId>micronaut-openapi</artifactId>
+              <version>${micronautopenapi.version}</version>
+            </path>
           </annotationProcessorPaths>
           <compilerArgs>
             <arg>-Amicronaut.processing.group=dev.amatos.restcountries</arg>

src/main/java/dev/amatos/restcountries/Application.java

@@ -2,6 +2,21 @@ package dev.amatos.restcountries;
 
 import io.micronaut.runtime.Micronaut;
 
+import io.swagger.v3.oas.annotations.OpenAPIDefinition;
+import io.swagger.v3.oas.annotations.info.Contact;
+import io.swagger.v3.oas.annotations.info.Info;
+import io.swagger.v3.oas.annotations.info.License;
+
+
+@OpenAPIDefinition(
+        info = @Info(
+                title = "rest-countries",
+                version = "3.1",
+                description = "Get information about countries via a RESTful API",
+                license = @License(name = "Mozilla Public License MPL 2.0", url = "https://www.mozilla.org/en-US/MPL/2.0/"),
+                contact = @Contact(url = "https://restcountries.com", name = "Alejandro Matos")
+        )
+)
 public class Application {
     public static void main(String[] args) {
         Micronaut.run(Application.class, args);