[meta] Support Kotlin meta generator (#4156)

* [meta] Support Kotlin meta generator

* Guard against automatic scripts (assumptions for this script are not fulfilled by some CI which run "run all" type scripts)

bin/meta-codegen-kotlin.sh

@@ -0,0 +1,52 @@
+#!/bin/sh
+
+SCRIPT="$0"
+echo "# START SCRIPT: $SCRIPT"
+
+if ! command -v gradle > /dev/null; then
+		echo "[WARN] This script requires a system gradle to be installed. Not treating this as an error."
+		exit 0
+fi
+
+while [ -h "$SCRIPT" ] ; do
+  ls=`ls -ld "$SCRIPT"`
+  link=`expr "$ls" : '.*-> \(.*\)$'`
+  if expr "$link" : '/.*' > /dev/null; then
+    SCRIPT="$link"
+  else
+    SCRIPT=`dirname "$SCRIPT"`/"$link"
+  fi
+done
+
+if [ ! -d "${APP_DIR}" ]; then
+  APP_DIR=`dirname "$SCRIPT"`/..
+  APP_DIR=`cd "${APP_DIR}"; pwd`
+fi
+
+executable="./modules/openapi-generator-cli/target/openapi-generator-cli.jar"
+
+if [ ! -f "$executable" ]
+then
+  ./mvnw -B clean package
+fi
+
+\rm -rf "samples/meta-codegen-kotlin/lib"
+
+export JAVA_OPTS="${JAVA_OPTS} -Xmx1024M -DloggerPath=conf/log4j.properties"
+ags="meta -n myClientCodegen -t DOCUMENTATION -p com.my.company.codegen -o samples/meta-codegen-kotlin/lib -l kotlin $@"
+
+java $JAVA_OPTS -jar $executable $ags
+
+if [ ! -f samples/meta-codegen-kotlin/gradle/wrapper/gradle-wrapper.jar ]; then
+  (cd samples/meta-codegen-kotlin/ && gradle wrapper --gradle-version 5.6.2 --distribution-type bin)
+fi
+
+
+(cp samples/meta-codegen-kotlin/gradlew samples/meta-codegen-kotlin/lib/ && \
+ cp -R samples/meta-codegen-kotlin/gradle samples/meta-codegen-kotlin/lib/ && \
+  cd samples/meta-codegen-kotlin/lib && \
+  ./gradlew shadowJar)
+
+ags2="generate -g myClientCodegen -i modules/openapi-generator/src/test/resources/2_0/petstore.json -o samples/meta-codegen-kotlin/usage $@"
+
+java $JAVA_OPTS -cp samples/meta-codegen-kotlin/lib/build/libs/my-client-codegen-openapi-generator-1.0-SNAPSHOT-all.jar:$executable org.openapitools.codegen.OpenAPIGenerator $ags2