[BUG] PlantUML generation produces a lot of warnings

Created by: typhoon2k

Bug Report Checklist

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

Description

When running plantuml generation we are getting a lot of these 2 warnings:

[main] WARN o.o.codegen.DefaultCodegen - escapeQuotationMark should be overridden in the code generator with proper logic to escape single/double quote [main] WARN o.o.codegen.DefaultCodegen - escapeUnsafeCharacters should be overridden in the code generator with proper logic to escape unsafe characters

openapi-generator version

5.0.0-beta

OpenAPI declaration file content or url

petstore.yaml can be used to repeat this problem.

Command line used for generation

    java \
        -jar openapi-generator-cli-5.0.0-beta.jar \
            generate \
            --input-spec $input_file \
            --generator-name plantuml \
            --output $output_folder

Steps to reproduce

1. run generator
2. check logs

Related issues/PRs

N/A

Suggest a fix

Provide overrides for escapeQuotationMark and escapeUnsafeCharacters.