✨ Add Salesforce source and Prefect tasks

[Diego-H-S]

Summary

Salesforce connector migration from viadot 1 to viadot 2.

Issue: #910

Importance

Required by the migration project.

Checklist

This PR:

• follows the guidelines laid out in CONTRIBUTING.md
• links relevant issue(s)
• adds/updates tests (if appropriate)
• adds/updates docstrings (if appropriate)
• adds an entry in CHANGELOG.md

[Diego-H-S]

have a look at the comments.

[trymzet]

Added my comments.

[trymzet]

@mgardzinski Can you pls rebase and make sure checks pass? Otherwise, it seems this is good to go.