feature(cSDK): Adding example for connecting to host using bastion server

[fivetran-sahilkhirwal]

Jira ticket

Closes https://fivetran.atlassian.net/browse/RD-978153

Description of Change

Adds example for connecting to source using the bastion server ( jump server )
The source is a postgreSQL database in this case

Testing

• EC2 instance with all traffic allowed for inbound and outbound traffic ( bastion host )
• EC2 instance with no Public IP, Inbound allowed only on port 22 and 5432 and for the bastion host IP
• PostgreSQL running on private EC2
• Data is fetched from the database using the Jump server using paramiko and sshtunnel using private key based authentication

Checklist

Some tips and links to help validate your PR:

• Tested the connector with fivetran debug command.
• Added/Updated example specific README.md file, refer here for template.
• Followed Python Coding Standards, refer here

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[Copilot]

Pull Request Overview

This PR adds a new example connector that demonstrates how to connect to a private PostgreSQL database through an SSH tunnel using a bastion server. The example implements SSH key-based authentication and incremental data synchronization based on timestamp tracking.

Key changes:

• Implements SSH tunneling with paramiko and sshtunnel libraries for secure database access
• Provides incremental sync functionality using modified_at timestamp column
• Includes comprehensive error handling for SSH and database connection issues

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
examples/common_patterns_for_connectors/bastion_server/requirements.txt	Specifies required dependencies for SSH tunneling and PostgreSQL connectivity
examples/common_patterns_for_connectors/bastion_server/connector.py	Main connector implementation with SSH tunnel setup and database operations
examples/common_patterns_for_connectors/bastion_server/configuration.json	Template configuration file with placeholder values for connection parameters
examples/common_patterns_for_connectors/bastion_server/README.md	Comprehensive documentation covering setup, configuration, and usage
README.md	Updates main README to include reference to the new bastion server example

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[fivetran-dejantucakov]

@fivetran-sahilkhirwal Please see suggestions.

[fivetran-satvikpatil]

Added minor comments, rest looks good.

[5tran-alexil]

README LGTM

[fivetran-dejantucakov]

LGTM