Bump Gerrit API to v3.9.0-rc0

Also bump Java version to 17, the one
supported for the Gerrit distribution.

Change-Id: I0be98b38fea16ba47a8aee64a8f5840e883c6c5d

README.md

diff --git a/README.md b/README.md
index 569c7b2..c497a89 100644
--- a/README.md
+++ b/README.md
@@ -78,13 +78,13 @@
 Gerrit 3.3 is distributed for Java 11 only. However, the source code is compatible
 with Java 8 assuming you build it from the source repository by yourself.
 
-The GitHub plugin can be built for Java 8 by using the `javaVersion=1.8` Maven
+The GitHub plugin can be built for Java 17 by using the `javaVersion=1.17` Maven
 parameter.
 
 Example:
   git clone https://gerrit.googlesource.com/plugins/github
   cd github
-  mvn -DjavaVersion=1.8 install
+  mvn -DjavaVersion=17 install
 
 ### singleusergroup plugin
 

github-oauth/pom.xml

diff --git a/github-oauth/pom.xml b/github-oauth/pom.xml
index 1f23fbb..d0594a3 100644
--- a/github-oauth/pom.xml
+++ b/github-oauth/pom.xml
@@ -21,7 +21,7 @@
   <parent>
     <groupId>com.googlesource.gerrit.plugins.github</groupId>
     <artifactId>github-parent</artifactId>
-    <version>3.8.2</version>
+    <version>3.9.0-rc0</version>
   </parent>
   <artifactId>github-oauth</artifactId>
   <name>Gerrit Code Review - GitHub OAuth login</name>

github-plugin/pom.xml

diff --git a/github-plugin/pom.xml b/github-plugin/pom.xml
index e635944..15cfa79 100644
--- a/github-plugin/pom.xml
+++ b/github-plugin/pom.xml
@@ -20,7 +20,7 @@
   <parent>
     <artifactId>github-parent</artifactId>
     <groupId>com.googlesource.gerrit.plugins.github</groupId>
-    <version>3.8.2</version>
+    <version>3.9.0-rc0</version>
   </parent>
 
   <artifactId>github-plugin</artifactId>

pom.xml

diff --git a/pom.xml b/pom.xml
index c397629..71dbe03 100644
--- a/pom.xml
+++ b/pom.xml
@@ -18,12 +18,12 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.googlesource.gerrit.plugins.github</groupId>
   <artifactId>github-parent</artifactId>
-  <version>3.8.2</version>
+  <version>3.9.0-rc0</version>
   <name>Gerrit Code Review - GitHub integration</name>
   <url>http://www.gerritforge.com</url>
   <packaging>pom</packaging>
   <properties>
-    <javaVersion>11</javaVersion>
+    <javaVersion>17</javaVersion>
   </properties>
   <licenses>
     <license>