[Feature Request]: Automatic OpenAPI 3.0 (OAS) Documentation Export for Web Services

## Description
Apache Hop’s **"Table to API"** functionality is already a game-changer — it allows rapid creation of APIs from data pipelines without complex coding. But, pointing in that direction, there’s an opportunity to take this feature to the next level and make Hop stand out even more in the ETL-Tool space.

When creating a Web Service in Hop to serve data, Hop already knows the structure, fields, types, and descriptions of the output. As well as the Parameters which must or can be provided to Filter the Data by different Functions or Fields.
This metadata is essentially an API contract — it just needs to be exported in **OpenAPI 3.0** format (OAS 3.0) to have a proper Documentation. Therefor the API can be set Produktive much more faster, because honestly speaking, it is always the Documentation which is laking while bringing things in Productive Environments :-)

## Why This Matters
- **Instant Integrations:** Many development teams require API documentation in OAS format before they can integrate with a service. If Hop could generate this automatically, an API created in the morning could be in production by the afternoon.
- **Avoid Manual Work:** Currently, teams have to recreate API specs manually, which is slow and error-prone. Hop can automate it perfectly since it already has the metadata.
- **Feature Parity with Leading Tools:** Other well-known ETL platforms ;-) have this built-in and it’s one of the reasons they’re adopted in enterprise environments. Adding it to Hop levels the playing field and even goes beyond, because Hop’s "Table to API" is already fast and intuitive.
- **Easier Maintenance:** If the schema changes, the documentation stays in sync automatically.

## Proposed Approach
- Extend the Web Service creation process to optionally output an **OAS 3.0 JSON/YAML** file alongside the service.
- Allow the user to add optional descriptions for the API, parameters, and fields directly in Hop’s UI.
- Support regenerating the OAS file whenever the pipeline or API configuration changes.

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With this in place, Apache Hop wouldn’t just create APIs quickly — it would also deliver the documentation needed to integrate them instantly in production environments, making Hop an even stronger choice for modern data engineering teams.

**Priority:** High – would significantly enhance adoption in integration-heavy environments.

### Issue Priority

Priority: 2

### Issue Component

Component: Other

Start by locating Hop’s Web Service creation flow and the existing “Table to API” functionality, then trace how output fields, types, descriptions, and filter parameters are represented. Done means an optional OpenAPI 3.0 JSON or YAML export can be generated and regenerated from the service metadata, with UI support for the proposed descriptions.

Written by the indexing model from the issue text.