On mac 'brew install postgresql' is required to use RDS features

[dbirman]

User story

When installing via pip install aind-data-access-api[rds] there is no obvious way to know that you need to have postgresql installed. An installation section in the README would clarify this

Acceptance criteria

• README or docs updated with installation instructions for Redshift features

Sprint Ready Checklist

• 1. Acceptance criteria defined
• 2. Team understands acceptance criteria
• 3. Team has defined solution / steps to satisfy acceptance criteria
• 4. Acceptance criteria is verifiable / testable
• 5. External / 3rd Party dependencies identified
• 6. Ticket is prioritized and sized

[dbirman]

On linux you have to do apt-get -y postgresql, might as well add that info too