[JavaSpring]swagger-codegen-maven-plugin with <async>false</async>

Hi,
I am using the swagger-codegen-maven-plugin with these versions: 2.3.1 and 2.4.0-SNAPSHOT (thats master i think).
I came across this bug. Please see code snippet below of the pom.xml alongwith my suggestions for the fix.. I think its not resolved yet.
If you feel its already fixed please excuse.
Thanks.
R
Please note value of asynch: false.

`

<groupId>io.swagger</groupId>
<artifactId>swagger-codegen-maven-plugin</artifactId>
<version>${swagger.codegen.version}</version>
<executions>
	<execution>
		<id>common</id>
		<goals>
			<goal>generate</goal>
		</goals>
		<configuration>
		<inputSpec>${project.basedir}/src/main/resources/api.yaml</inputSpec>
			<modelPackage>com.example.api.models</modelPackage>
			<apiPackage>com.example.api</apiPackage>
			<output>${project.basedir}</output>					
			<language>spring</language>
			<invokerPackage>com.example.api</invokerPackage>
			<basePackage>com.example.api</basePackage>
			<withXml>true</withXml>
			<configOptions>
				<artifactId>foo</artifactId>
				<artifactDescription>Test API</artifactDescription>
				<title>Test API</title>
				<artifactUrl>https://api.example.com</artifactUrl>
				<groupId>com.example.api</groupId>
				<artifactVersion>1</artifactVersion>								
				<sourceFolder>src/gen/java/main</sourceFolder>
				<serializableModel>true</serializableModel>
				<dateLibrary>java8</dateLibrary>
				<java8>true</java8>
				<async>false</async>
				<library>spring-boot</library>		
				<delegatePattern>true</delegatePattern>
				<useBeanValidation>true</useBeanValidation>
				<useOptional>true</useOptional>	
				<hideGenerationTimestamp>true</hideGenerationTimestamp>								
			</configOptions>							
		</configuration>
	</execution>
</executions>

For the above configuration in swagger-codegen\src\main\resources\JavaSpring\apiDelegate.mustache an expression of {{#async}}CompletableFuture.completedFuture({{/async}} should resolve to empty. Unfortunately : In swagger-codegen\src\main\java\io\swagger\codegen\DefaultGenerator.java the value of async in this.config.additionalProperties() is a string.

This causes wrong code generation.

I can think of three solutions:

1. In swagger-codegen\src\main\java\io\swagger\codegen\languages\SpringCodegen.java in public void processOpts() method change these lines:
   if (additionalProperties.containsKey(ASYNC)) {
   this.setAsync(Boolean.valueOf(additionalProperties.get(ASYNC).toString()));
   }
   TO
   if (additionalProperties.containsKey(ASYNC)) {
   this.setAsync(Boolean.valueOf(additionalProperties.get(ASYNC).toString()));
   convertPropertyToBooleanAndWriteBack(ASYNC);
   }

2. Another way is in swagger-codegen\src\main\java\io\swagger\codegen\DefaultGenerator.java in method public Generator opts(ClientOptInput opts) right after this line
   "this.config = opts.getConfig();"
   invoke
   'adjustToBoolean("async");'
   this second approach has benefit that you can use it from one place than do this change from many places.
   I also think there may be other similar boolean properties that need similar handling.
   //new method

`
public void adjustToBoolean(String propertyName)
{
Object object = this.config.additionalProperties().get(propertyName);
Boolean val=Boolean.FALSE;
if(object!=null)
{
if(object instanceof String)
{
String string=(String) object;
if(string.equalsIgnoreCase("true"))
{
val=true;
}
else
{
val=Boolean.FALSE;
}
}
else if(object instanceof Boolean)
{
val=(Boolean) object;
}
else
{
val=Boolean.TRUE;
}
}
else
{
val=Boolean.FALSE;
}
this.config.additionalProperties().put(propertyName, val);

} 

`
Adding a a small google doc with more details using the 2nd approach
https://docs.google.com/document/d/1N7ASyYPAuk5gO_kqcggXHOG_w5nGlKlToy2H1bbG6Tg/edit?usp=sharing

3. A third approach could be to eliminate the booleans like false being created as strings in the first place. That is something havent pursued.

Start with swagger-codegen/src/main/java/io/swagger/codegen/DefaultGenerator.java and languages/SpringCodegen.java, then inspect swagger-codegen/src/main/resources/JavaSpring/apiDelegate.mustache. Trace how the Maven plugin's async value reaches additionalProperties. Done means generating the shown Spring configuration with async=false no longer emits CompletableFuture.completedFuture code.