feat: python version of idp-sql tutorial

[glasnt]

Description

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.6 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• Please merge this PR for me once it is approved.

[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• run/idp-sql/credentials.py:24, tag cloudrun_user_auth_secrets
• run/idp-sql/database.py:95, tag cloudrun_user_auth_sql_connect
• run/idp-sql/middleware.py:28, tag cloudrun_user_auth_jwt

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[averikitsch]

A few thoughts:

1. Is there an idiomatic way to split main.py into separate files to reduce complexity?
2. A priority is to add a sig term handler to show of that functionality (depending on this postgres library, the db connections can be closed when sigterm is caught)
3. A lesser priority would be to implement better logging. In order for stackdriver to parse the logs correctly they need to be json formatted with a severity property to set for the log level to be parsed.

[glasnt]

As discussed with @averikitsch, this now uses NullPool when testing only to work around service delete issues; will re-address when upstream changes happen around those. I'm comfortable with this PR being merged as it is.

(I have the ability to hit the [squash and merge] button with the approvals received, but I'm not sure if I should be merging my own PRs)

[averikitsch]

As discussed with @averikitsch, this now uses NullPool when testing only to work around service delete issues; will re-address when upstream changes happen around those. I'm comfortable with this PR being merged as it is.

(I have the ability to hit the [squash and merge] button with the approvals received, but I'm not sure if I should be merging my own PRs)

LGTM. Feel free to merge