[Issue #1519] Cherry pick platform's pattern for env vars & ssm secrets

[coilysiren]

Summary

Relates to #784

Closes #1519

Copies navapbc/template-infra#549

Time to review: 10 mins

Changes proposed

• cherry picks platform infra template's pattern for passing in env vars and AWS SSM secrets
• changes ENABLE_V_0_1_ENDPOINTS / enable_v01_endpoints to use the above pattern
• does not yet change any of our SSM secrets to use platform's pattern, I plan to do that in a follow-up PR

Context for reviewers

I created this PR via tactical copy-pasting from the https://github.com/navapbc/template-infra/ repo.

The goal of this PR is to DRY our methods for setting environment variables. Notice on the red side of the diff, how I've removed the need to set enable_v01_endpoints so many times. Then notice on the green side of the diff, that I only need to set ENABLE_V_0_1_ENDPOINTS twice (for dev and staging). That's the goal of this PR, to pull in platform's very nice pattern for DRY'ing environment variables.

Testing

To test this, I added - then removed - the following block from staging.tf

  service_override_extra_environment_variables = {
    ENABLE_V_0_1_ENDPOINTS = "true"
  }

I then deployed to staging to see the difference. It worked as intended.

[coilysiren]

https://github.com/navapbc/template-infra/blob/main/docs/infra/environment-variables-and-secrets.md

[coilysiren]

The CI failures are related to the WAF. They dont seem related to this PR

[chouinar]

Looks good, at least to my rough understanding of terraform

[chouinar]

Could we add the ENABLE_V_0_1_ENDPOINTS value in the service overrides as false?

Doesn't technically need to be there (null == false for this), but just to have the mapping defined for prod.

[coilysiren]

@chouinar I wanted to leave it null since the string "False" is truthy, ya know?

$ python -c 'print(bool("False"))'
> True

Unless you're certain the that thing reading the env vars is casting strings to booleans "properly"!

[chouinar]

We use Pydantic for loading env vars / converting to Python types. It considers false as a false value: https://docs.pydantic.dev/2.0/usage/types/booleans/

[coilysiren]

Added! f32edb6

[coilysiren]

I was able to confirm that the terratest CI failures (eg. Infra Service Checks) aren't related to this PR. This example PR reproduces the same failures: #1522