[OpenAPI Generator] Enable custom `operationId -> name` mapping

[newtork]

Usage:

• In additionalProperties define operationIdNames. Use <space> or , as entry delimiter. Use = to separate key value.

<plugin>
  <groupId>com.sap.cloud.sdk.datamodel</groupId>
  <artifactId>openapi-generator-maven-plugin</artifactId>
  <configuration>
    <additionalProperties>
      <operationIdNames>
        getSodaById=getById
      </operationIdNames>
    </additionalProperties>