[BUG] Server URL '/' removed from inputs to generator

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

A URL of / in the servers section of an OpenAPI 3 document is replaced with the empty string

openapi-generator version

Gradle plug-in 5.3.0 (also recreated in latest code)

OpenAPI declaration file content or url

...
servers:
   url: /
   description: An API handing off the root of the server
...

Generation Details

openapi-generator generate -i src/main/api/openapi.yaml --library openliberty -t ~/custom-template -g jaxrs-spec --global-property debugSupportingFiles

Steps to reproduce

Use a template that uses {{servers.0.url}} in the files.

Related issues/PRs

The behaviour appears to have been added as part of #7533 where trailing slashes were being removed from the servers.

Suggest a fix

Will raise a PR to add code to only remove the trailing / if there are characters preceding it.

Reproduce the issue with the shown OpenAPI YAML and the openapi-generator generate command, using a template that references {{servers.0.url}}. Read the server URL handling introduced by #7533. Done means a root URL of / remains /, while trailing-slash removal still applies when characters precede the slash.