turn build time warnings into errors

Signed-off-by: Lukas Jungmann <lukas.jungmann@oracle.com>

api/pom.xml

diff --git a/api/pom.xml b/api/pom.xml
index 58d9999..4395bb1 100644
--- a/api/pom.xml
+++ b/api/pom.xml
@@ -273,6 +273,7 @@
                     <compilerArgs>
                         <arg>-Xlint:all</arg>
                         <arg>-Xdoclint:all</arg>
+                        <arg>-Werror</arg>
                     </compilerArgs>
                     <showDeprecation>true</showDeprecation>
                     <showWarnings>true</showWarnings>