adding a lambda handler and client for database access

[aaarendt]

Overview

This PR has scripts to deploy a Python handler to AWS Lambda that leverages native functionality of the existing api. The geospatial heavy operations require large libraries that were too cumbersome for Lambda, so many changes are implemented here to simplify and avoid use of geopandas. This includes relying on PostGIS functionality at the db backend, and relying on the client side to query geometries and convert back to geospatial objects, thereby avoiding needing geopandas in the Lambda handler itself.

Performance issues were discovered along the way since this is the first time doing operations on the 29 GB layers table. Specifically, all_instruments query should use EXISTS instead of DISTINCT with join which vastly improves performance.

Throughout I updated the handling of credentials following #204 .
This code was primarily developed using AI-assistance.

[codecov]

Codecov Report

❌ Patch coverage is 43.10954% with 322 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.68%. Comparing base (f8af2f8) to head (98b83ac).

Files with missing lines	Patch %	Lines
snowexsql/lambda_client.py	11.46%	193 Missing ⚠️
snowexsql/lambda_handler.py	64.22%	78 Missing ⚠️
snowexsql/api.py	60.76%	51 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #206       +/-   ##
===========================================
- Coverage   75.88%   59.68%   -16.20%     
===========================================
  Files          21       23        +2     
  Lines         651     1146      +495     
===========================================
+ Hits          494      684      +190     
- Misses        157      462      +305     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.