Update samples to Spring Boot 4.0.0-SNAPSHOT

Closes gh-2091

samples/backend-for-spa-client/samples-backend-for-spa-client.gradle

@@ -1,5 +1,5 @@
 plugins {
-	id "org.springframework.boot" version "3.2.2"
+	id "org.springframework.boot" version "4.0.0-SNAPSHOT"
 	id "io.spring.dependency-management" version "1.1.0"
 	id "java"
 }
@@ -18,7 +18,7 @@ repositories {
 }
 
 ext {
-	set("springCloudVersion", "2023.0.2")
+	set("springCloudVersion", "2025.1.0-SNAPSHOT")
 }
 
 dependencyManagement {

samples/default-authorizationserver/samples-default-authorizationserver.gradle

@@ -1,5 +1,5 @@
 plugins {
-	id "org.springframework.boot" version "3.4.3"
+	id "org.springframework.boot" version "4.0.0-SNAPSHOT"
 	id "io.spring.dependency-management" version "1.1.0"
 	id "java"
 }

samples/demo-authorizationserver/samples-demo-authorizationserver.gradle

@@ -1,5 +1,5 @@
 plugins {
-	id "org.springframework.boot" version "3.4.3"
+	id "org.springframework.boot" version "4.0.0-SNAPSHOT"
 	id "io.spring.dependency-management" version "1.1.0"
 	id "java"
 }

samples/demo-client/samples-demo-client.gradle

@@ -1,5 +1,5 @@
 plugins {
-	id "org.springframework.boot" version "3.2.2"
+	id "org.springframework.boot" version "4.0.0-SNAPSHOT"
 	id "io.spring.dependency-management" version "1.1.0"
 	id "java"
 }

samples/messages-resource/samples-messages-resource.gradle

@@ -1,5 +1,5 @@
 plugins {
-	id "org.springframework.boot" version "3.2.2"
+	id "org.springframework.boot" version "4.0.0-SNAPSHOT"
 	id "io.spring.dependency-management" version "1.1.0"
 	id "java"
 }

samples/users-resource/samples-users-resource.gradle

@@ -1,12 +1,15 @@
 plugins {
-	id "org.springframework.boot" version "3.2.2"
+	id "org.springframework.boot" version "4.0.0-SNAPSHOT"
 	id "io.spring.dependency-management" version "1.1.0"
 	id "java"
 }
 
 group = project.rootProject.group
 version = project.rootProject.version
-sourceCompatibility = "17"
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_17
+}
 
 repositories {
 	mavenCentral()

samples/x509-certificate-generator/samples-x509-certificate-generator.gradle

@@ -1,5 +1,5 @@
 plugins {
-	id "org.springframework.boot" version "3.2.2"
+	id "org.springframework.boot" version "4.0.0-SNAPSHOT"
 	id "io.spring.dependency-management" version "1.1.0"
 	id "java"
 }
@@ -13,6 +13,8 @@ java {
 
 repositories {
 	mavenCentral()
+	maven { url "https://repo.spring.io/milestone" }
+	maven { url "https://repo.spring.io/snapshot" }
 }
 
 dependencies {

settings.gradle

@@ -1,6 +1,9 @@
 pluginManagement {
 	repositories {
 		gradlePluginPortal()
+		mavenCentral()
+		maven { url "https://repo.spring.io/milestone" }
+		maven { url "https://repo.spring.io/snapshot" }
 	}
 }