quarkus.openapi.generator.spec only supports one json-file

[jlistemann-ish]

When setting up a new project server, the creation of multiple spec files does not work.

• Generated just the latest file:

quarkus.openapi.generator.spec=order-management-communication-2.11.json
quarkus.openapi.generator.spec=iom-gdpr-2x9x4x0.json

Generated nothing:

• CSV:

quarkus.openapi.generator.spec=order-management-communication-2.11.json,iom-gdpr-2x9x4x0.json

• INDEX:

quarkus.openapi.generator.spec[0]=order-management-communication-2.11.json
quarkus.openapi.generator.spec[1]=iom-gdpr-2x9x4x0.json

Refer https://docs.quarkiverse.io/quarkus-openapi-generator/dev/server.html