Spring Boot 3 migration (#255)

* It compiles

* WIP

* Upgraded jdk to 17:

* Added tests for Github repo

* Modified the sagan client

* Updated versions

projects/spring-cloud-stream/pom.xml

@@ -10,13 +10,13 @@
 	<parent>
 		<groupId>org.springframework.cloud.internal</groupId>
 		<artifactId>releaser-projects</artifactId>
-		<version>2.0.0-SNAPSHOT</version>
+		<version>3.0.0-SNAPSHOT</version>
 		<relativePath>..</relativePath>
 	</parent>
 
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-		<java.version>1.8</java.version>
+		<java.version>17</java.version>
 	</properties>
 
 	<dependencies>