Add SSH/SFTP support for ObjectStoragePath

[anishgirianish]

---

Summary

Adds SSH/SFTP protocol support for Airflow's ObjectStoragePath
abstraction, enabling file operations over SFTP using existing Airflow
connections.

• Implements get_fs() function using the sshfs library
  (fsspec-compatible)
• Supports sftp:// and ssh:// URI schemes
• Integrates with existing SFTP connection configuration (host, port,
  credentials, key files)

Usage

from airflow.sdk import ObjectStoragePath                              
                                                                       
# Read/write files over SFTP                                           
path = ObjectStoragePath("sftp://my_sftp_conn@server/path/to/file.txt")
content = path.read_text()                                             
                                                                       
# Copy between backends                                                
path.copy(ObjectStoragePath("s3://aws_conn@bucket/file.txt"))          
                                                                                                                               

Changes

• providers/sftp/src/airflow/providers/sftp/fs/sftp.py - Core
  implementation
• providers/sftp/tests/unit/sftp/fs/test_sftp.py - Unit tests
• providers/sftp/provider.yaml - Register filesystem
• providers/sftp/pyproject.toml - Add sshfs optional dependency
• providers/sftp/docs/filesystems/sftp.rst - Documentation

Installation

pip install apache-airflow-providers-sftp[sshfs]

closes: #60558

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[fritz-astronomer]

lgtm.
I see lots of tests for connection parsing, and I was going to comment about having an integration test - but I suppose as long as the connection is passed as expected, sshfs is going to handle all that.

Were you able to do a full test with an SSH/SFTP system?

[anishgirianish]

lgtm. I see lots of tests for connection parsing, and I was going to comment about having an integration test - but I suppose as long as the connection is passed as expected, sshfs is going to handle all that.

Were you able to do a full test with an SSH/SFTP system?

Thanks for the review, @fritz-astronomer! Yes, I spun up a local SFTP server with Docker and ran through the
basic operations - reads, writes, listing, deletes all worked fine.

[anishgirianish]

Hi @bolkedebruin, hope you're doing well. I would like to request your review on this PR when you have a moment. Please take your time, and I truly appreciate any feedback you might have. Thank you so much - it means a lot! 🙏