deps: upgrade Spring Boot and other dependencies

Author: mrts

example/pom.xml

@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-parent</artifactId>
-		<version>2.2.5.RELEASE</version>
+		<version>2.6.5</version>
 		<relativePath/> <!-- lookup parent from repository -->
 	</parent>
 	<groupId>org.webeid.example</groupId>
@@ -29,6 +29,10 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-web</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-validation</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-thymeleaf</artifactId>
@@ -45,18 +49,18 @@
 		<dependency>
 			<groupId>com.google.guava</groupId>
 			<artifactId>guava</artifactId>
-			<version>30.1-jre</version>
+			<version>31.1-jre</version>
 		</dependency>
 		<dependency>
 			<groupId>com.squareup.okhttp3</groupId>
 			<artifactId>okhttp</artifactId>
-			<version>4.9.0</version>
+			<version>4.9.3</version>
 		</dependency>
 
 		<dependency>
 			<groupId>org.digidoc4j</groupId>
 			<artifactId>digidoc4j</artifactId>
-			<version>4.1.1</version>
+			<version>4.3.0</version>
 		</dependency>
 		<dependency>
 			<groupId>org.webeid.security</groupId>

example/src/main/resources/application.yaml

@@ -1,3 +1,7 @@
+spring:
+  main:
+    allow-circular-references: true
+
 # Make session cookie secure behind a reverse proxy, see
 # - https://docs.spring.io/spring-boot/docs/2.2.5.RELEASE/reference/htmlsingle/#howto-use-behind-a-proxy-server
 # - https://docs.spring.io/spring-boot/docs/2.2.5.RELEASE/reference/htmlsingle/#howto-enable-https