remove unused import org.openapitools.jackson.nullable.JsonNullable from generated model

Created by: pellyadolfo

Bug Report Checklist

• [ X] Have you provided a full/minimal spec to reproduce the issue?
• [ X] Have you validated the input using an OpenAPI validator (example)?
• [ X] What's the version of OpenAPI Generator used?
• [ X] Have you search for related issues/PRs?
• [X ] What's the actual output vs expected output?
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Description

When I generate the model there is an unused import org.openapitools.jackson.nullable.JsonNullable; in every single DTO. It forces me to add a dependency.

	<dependency>
	    <groupId>org.openapitools</groupId>
	    <artifactId>jackson-databind-nullable</artifactId>
	    <version>0.1.0</version>
	</dependency>

Unfortunately this dependency must be approved in the company so the model is unusable.

Is there any way to get rid of this unused import? Configuration is below:

		<plugin>
		    <groupId>org.openapitools</groupId>
		    <artifactId>openapi-generator-maven-plugin</artifactId>
		    <version>4.0.0</version>
		    <executions>
		        <execution>
		            <goals>
    			        <goal>generate</goal>
    			    </goals>
        			<configuration>
				<inputSpec>${maven.multiModuleProjectDirectory}/api/target/generated/swagger-api-spec/swagger.json</inputSpec>	
					<language>spring</language>
					<library>spring-boot</library>
					<model-name-prefix>Cqrs</model-name-prefix>
					<modelPackage>com.anthem.specialty.provider.springapi.model</modelPackage>
					<apiPackage>com.anthem.specialty.provider.springapi.api</apiPackage>
					<invokerPackage>com.anthem.specialty.provider.springapi.invoker</invokerPackage>
        			    <skipValidateSpec>true</skipValidateSpec>
					<generateSupportingFiles>true</generateSupportingFiles>
					<supportingFilesToGenerate>
						ApiApi.java,ApiApiControler.java,ApiUtil.java
					</supportingFilesToGenerate>
        			    <configOptions>
					<sourceFolder>src/gen/java/main</sourceFolder>
					<java8>false</java8>
					<dateLibrary>java8</dateLibrary>
					<interfaceOnly>false</interfaceOnly>
					<groupId>com.company</groupId>
					<artifactId>${project.artifactId}</artifactId>
					<artifactVersion>${project.version}</artifactVersion>
        		    		</configOptions>
        			</configuration>
	        	</execution>
		    </executions>
		</plugin>	

openapi-generator version

		    <groupId>org.openapitools</groupId>
		    <artifactId>openapi-generator-maven-plugin</artifactId>
		    <version>4.0.0</version>

OpenAPI declaration file content or url

probably convenient enhancement

Command line used for generation

maven plugin

Steps to reproduce

run the maven clean install

Related issues/PRs

a few similar issues

Suggest a fix

provide a mechanism to remove unused imports