Codegen maven plugin cannot generate "meta" generator

Description

Codegen maven plugin does not expose "meta" command line execution mode.

Swagger-codegen version

3.0.30

Swagger declaration file content or url

Irrelevant

Command line used for generation

Irrelevant

Steps to reproduce

Use the following plugin configuration

            
            <plugin>
                <groupId>io.swagger.codegen.v3</groupId>
                <artifactId>swagger-codegen-maven-plugin</artifactId>
                <version>3.0.30</version>
                <configuration>
                    <language>meta</language>
                    <inputSpec></inputSpec>
                </configuration>
            </plugin>

and run generate goal.

Related issues/PRs

Irrelevant

Suggest a fix/enhancement

Make sure that the maven plugin is just an integration point, much like the cli jar is rather than implement logic in them.

Start with the swagger-codegen Maven plugin's generate goal and the command-line execution mode it exposes. Trace how the language value is passed when it is set to meta; done means the plugin can run the meta generator with the shown configuration and its behavior is covered by the project's relevant checks.