Upgrade Spring Framework to 5.3.0-M1

Closes gh-1649

Author: eleftherias

gradle/dependency-management.gradle

@@ -2,7 +2,7 @@ dependencyManagement {
 	imports {
 		mavenBom 'io.projectreactor:reactor-bom:Dysprosium-SR9'
 		mavenBom 'org.junit:junit-bom:5.6.2'
-		mavenBom 'org.springframework:spring-framework-bom:5.2.6.RELEASE'
+		mavenBom 'org.springframework:spring-framework-bom:5.3.0-M1'
 		mavenBom 'org.springframework.data:spring-data-releasetrain:Neumann-RELEASE'
 		mavenBom 'org.springframework.security:spring-security-bom:5.3.3.RELEASE'
 		mavenBom 'org.testcontainers:testcontainers-bom:1.14.3'

spring-session-samples/spring-session-sample-javaconfig-rest/spring-session-sample-javaconfig-rest.gradle

@@ -22,4 +22,5 @@ dependencies {
 
 gretty {
 	jvmArgs = ['-Dspring.profiles.active=embedded-redis']
+	servletContainer = 'tomcat9'
 }