Perform a release

Because we do not want to perform a lot of releases from this fork, the support for release is not made in TravisCI.

Here is how to perform a release:

Create a commit that change the version -SNAPSHOT to a fix version (example 2.0.2-SNAPSHOT changed to 2.0.2-OpenAPITools.org-1).

Push and tag this commit. The CI on Travis will fail.

Locally run maven to build, sign and deploy the artifacts:

export OPENAPITOOLS_SONATYPE_USERNAME=<insert>
export OPENAPITOOLS_SONATYPE_PASSWORD=<insert>
export SIGNING_PASSPHRASE='<insert>'
export SIGNING_KEY=<insert something liek AB98CD12>

# VERIFY that signing works:
mvn verify -P release --settings .travis/settings.xml -Dgpg.passphrase=$SIGNING_PASSPHRASE -Dgpg.keyname=$SIGNING_KEY

# DEPLOY on maven central:
mvn deploy -P release --settings .travis/settings.xml -Dgpg.passphrase=$SIGNING_PASSPHRASE -Dgpg.keyname=$SIGNING_KEY

Set the version back to the -SNAPSHOT version (no upgrade, we want to say in sync with the official project), commit and push.