Currently the language selection for openzaak documentapi document uploads is limited to 3 languages: - Dutch - English - German  The values for this dropdown are hardcoded[ in the valtimo frontend libraries](https://github.com/valtimo-platform/valtimo-frontend-libraries/blob/c0604eecb123b76c2c55913d04a392f72e53f32e/projects/valtimo/zgw/src/lib/modules/documenten-api/components/documenten-api-metadata-modal/documenten-api-metadata-modal.component.ts#L388). `public readonly LANGUAGES: Array<DocumentLanguage> = ['nld', 'eng', 'deu'];` These values should somehow be configurable so different languages can be used.