…or schema

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[X] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #1073

The ApiBody decorator does not allow to add an examples section
and the schema option does not allow to use a $ref

The issue that @Body overrides all this information from the @ApiOperations
decorator is still an issue, but defining this information in the ApiBody is a
good workaround

What is the new behavior?

The ApiBody uses the examples section and allow a $ref type.

Does this PR introduce a breaking change?

[ ] Yes
[X] No