Add OSOP workflow example — ETL pipeline in portable format

[Archie0125]

Summary

• Adds an OSOP (Open Standard for Orchestration Protocols) workflow example under examples/osop/
• The example models a typical ETL pipeline: extract CSV from cloud storage, validate schema, transform data, load in parallel to PostgreSQL and BigQuery, with error notifications
• Includes a README explaining the OSOP format and how to validate/visualize the workflow

What is OSOP?

OSOP is a portable YAML-based workflow standard — think "OpenAPI for workflows." It lets you describe multi-step processes (including data pipelines and orchestration flows) in a tool-agnostic format that any orchestration engine can read.

• OSOP Spec
• OSOP Examples

Why this PR?

This is a non-invasive, additive-only contribution. The .osop file provides a portable representation of a Kestra-style ETL pipeline that can be shared, diffed, and rendered by any OSOP-compatible tool — useful for documentation, onboarding, and cross-tool interoperability.

No existing files are modified.

[github-actions]

Hey @Archie0125 👋

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[loicmathieu]

We didn't support osop and I cannot see the value for an example of an osop format workflow inside Kestra.
If you want Kestra to support or interop with osop, please open an issue about it.