Add language validation & refactor config initialization

pom.xml

@@ -16,6 +16,12 @@
             <resource>
                 <directory>src/main/resources</directory>
             </resource>
+            <resource>
+                <directory>./</directory>
+                <includes>
+                    <include>language-codes</include>
+                </includes>
+            </resource>
         </resources>
         <testResources>
             <testResource>
@@ -76,8 +82,8 @@
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <configuration>
-                    <source>9</source>
-                    <target>9</target>
+                    <source>11</source>
+                    <target>11</target>
                 </configuration>
             </plugin>
         </plugins>