fix: always use API_V3_URL environment variable

[sloanelybutsurely]

Our ECS tasks all set a API_V3_URL pointing to the desired V3 API environment but we were ignoring that value and instead deriving the V3 API URL based on ENVIRONMENT_NAME. This is confusing.

With this change the URL used for the V3 API is always fetched from the environment as API_V3_URL (unless MIX_ENV=test).

This has the added benefit of picking up the changes in https://github.com/mbta/devops/pull/2122

Asana task: Point screens-dev-green at api-dev-blue

[digitalcora]

Seems odd that we have two ways of doing this. If we have API_V3_URL in deployed environments, any reason we shouldn't just always look at that, and delete this extra condition based on ENVIRONMENT_NAME?

[sloanelybutsurely]

@digitalcora that's a great point! we do have this as an environment variable in prod, dev, and dev-green. i'll go ahead and refactor this code to always use API_V3_URL.

---

the signs_ui s3 bucket is also configured based on ENVIRONMENT_NAME but those values are available as a terraform variable (would require exposing them via environment variable in the ECS task definition). i'll open separate PRs for those changes.

screens/config/runtime.exs

Lines 28 to 34 in c7d9904

	signs_ui_s3_bucket =
	case eb_env_name do
	"screens-prod" -> "mbta-signs"
	"screens-dev" -> "mbta-signs-dev"
	"screens-dev-green" -> "mbta-signs-dev"
	_ -> nil
	end

[digitalcora]

I suppose we could also say that ENVIRONMENT_NAME is the one true way, and derive everything from that. Advantage would be that it doesn't require Terraform changes to change how our environments are connected. But then that's kind of putting "infrastructural" data in the app code.

[sloanelybutsurely]

I suppose we could also say that ENVIRONMENT_NAME is the one true way, and derive everything from that. Advantage would be that it doesn't require Terraform changes to change how our environments are connected. But then that's kind of putting "infrastructural" data in the app code.

@digitalcora my preference is to always use the environment variables for each individual parameter. this keeps that kind of configuration in terraform as a single source of truth for connections between applications

[cmaddox5]

Sorry for missing what Cora caught. And thanks for fixing it.