Upgrade to spring boot 2.3.1 (#154)

Upgrade to Spring Boot 2.3.1.RELEASE

pom.xml

@@ -6,12 +6,12 @@
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
-        <version>2.2.8.RELEASE</version>
+        <version>2.3.1.RELEASE</version>
     </parent>
 
     <groupId>org.springframework.samples</groupId>
     <artifactId>spring-petclinic-microservices</artifactId>
-    <version>2.2.8</version>
+    <version>2.3.1</version>
     <name>${project.artifactId}</name>
     <packaging>pom</packaging>
 
@@ -29,7 +29,7 @@
         <java.version>1.8</java.version>
         <assertj.version>3.11.1</assertj.version>
 
-        <spring-boot.version>2.2.8.RELEASE</spring-boot.version>
+        <spring-boot.version>2.3.1.RELEASE</spring-boot.version>
         <spring-cloud.version>Hoxton.SR5</spring-cloud.version>
 
         <maven-surefire-plugin.version>2.22.0</maven-surefire-plugin.version>

spring-petclinic-admin-server/pom.xml

@@ -12,7 +12,7 @@
     <parent>
         <groupId>org.springframework.samples</groupId>
         <artifactId>spring-petclinic-microservices</artifactId>
-        <version>2.2.8</version>
+        <version>2.3.1</version>
     </parent>
 
     <properties>

spring-petclinic-api-gateway/pom.xml

@@ -11,7 +11,7 @@
     <parent>
         <groupId>org.springframework.samples</groupId>
         <artifactId>spring-petclinic-microservices</artifactId>
-        <version>2.2.8</version>
+        <version>2.3.1</version>
     </parent>
 
     <properties>

spring-petclinic-config-server/pom.xml

@@ -11,7 +11,7 @@
     <parent>
         <groupId>org.springframework.samples</groupId>
         <artifactId>spring-petclinic-microservices</artifactId>
-        <version>2.2.8</version>
+        <version>2.3.1</version>
     </parent>
 
     <properties>

spring-petclinic-customers-service/pom.xml

@@ -11,7 +11,7 @@
 	<parent>
 		<groupId>org.springframework.samples</groupId>
 		<artifactId>spring-petclinic-microservices</artifactId>
-		<version>2.2.8</version>
+		<version>2.3.1</version>
 	</parent>
 
     <properties>

spring-petclinic-discovery-server/pom.xml

@@ -11,7 +11,7 @@
     <parent>
         <groupId>org.springframework.samples</groupId>
         <artifactId>spring-petclinic-microservices</artifactId>
-        <version>2.2.8</version>
+        <version>2.3.1</version>
     </parent>
 
     <properties>

spring-petclinic-vets-service/pom.xml

@@ -11,7 +11,7 @@
 	<parent>
 		<groupId>org.springframework.samples</groupId>
 		<artifactId>spring-petclinic-microservices</artifactId>
-		<version>2.2.8</version>
+		<version>2.3.1</version>
 	</parent>
 
     <properties>

spring-petclinic-visits-service/pom.xml

@@ -11,7 +11,7 @@
     <parent>
         <groupId>org.springframework.samples</groupId>
         <artifactId>spring-petclinic-microservices</artifactId>
-        <version>2.2.8</version>
+        <version>2.3.1</version>
     </parent>
 
     <properties>