[Docker] Dockerfile build error: module swagger-generator is missing

Description

The dockerfile removes the generation of the swagger-generator, which produces "module not found" compilation error when the docker file is run alone.

@jimschubert was there a specific reason why you explicitly removed it?

# NOTE: swagger-generator is not included here, it is available as swaggerapi/swagger-generator

The Dockerfile really should run on it's own, so without going through one of the building platforms as it makes contributing a lot (I cannot state this enough) easier for those of us who do not originally code in java

Swagger-codegen version

master

Command line used for generation

Docker build alone so:

docker build .

Steps to reproduce

checkout master and run docker build .

Suggest a fix/enhancement

Dockerfile

FROM jimschubert/8-jdk-alpine-mvn:1.0

RUN set -x && \
    apk add --no-cache bash

ENV GEN_DIR /opt/swagger-codegen
WORKDIR ${GEN_DIR}
VOLUME  ${MAVEN_HOME}/.m2/repository

# Required from a licensing standpoint
COPY ./LICENSE ${GEN_DIR}

# Required to compile swagger-codegen
COPY ./google_checkstyle.xml ${GEN_DIR}

# Modules are copied individually here to allow for caching of docker layers between major.minor versions
COPY ./modules/swagger-codegen-maven-plugin ${GEN_DIR}/modules/swagger-codegen-maven-plugin
COPY ./modules/swagger-codegen-cli ${GEN_DIR}/modules/swagger-codegen-cli
COPY ./modules/swagger-codegen ${GEN_DIR}/modules/swagger-codegen
COPY ./modules/swagger-generator ${GEN_DIR}/modules/swagger-generator
COPY ./pom.xml ${GEN_DIR}

# Pre-compile swagger-codegen-cli
RUN mvn -am -pl "modules/swagger-codegen-cli" package

# This exists at the end of the file to benefit from cached layers when modifying docker-entrypoint.sh.
COPY docker-entrypoint.sh /usr/local/bin/

ENTRYPOINT ["docker-entrypoint.sh"]

CMD ["help"]

Start with the repository Dockerfile and reproduce the issue using docker build . from the repository root. Check how the listed modules are copied and how Maven builds the CLI, then verify that a standalone Docker build no longer reports the missing swagger-generator module.