Source Hubspot: ensure best practices are applied (rate limiting, tests all streams etc.)

[eugene-kulak]

Tell us about the problem you're trying to solve

What are you trying to do, and why is it hard? A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

Describe the solution you’d like

• add backoff to get/post requests
• implement health_check method
• test scenarios with invalid creds, permissions, etc and ensure User will see a meaningful/actionable error message
• update docs