Add tests to update and delete environment vars

[klutchell]

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PR Overview

This PR adds test coverage for updating and deleting environment variables and refines the handling of API requests in the Environments plugin.

• Added tests to detect divergence when environment variables require updates or deletion.
• Adjusted filtering logic and API request handling in lib/plugins/environments.js to support the new behaviors.

Reviewed Changes

File	Description
test/unit/lib/plugins/environments.test.js	Added tests for updating and deleting environment variables.
lib/plugins/environments.js	Updated API request calls, filtering logic for variable updates, and minor code formatting improvements.

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

lib/plugins/environments.js:178

• [nitpick] Confirm that updating existingVariables by filtering out variables with matching names (using !==) is the intended behavior to avoid deleting variables that have been processed during an update. Additionally, verify that the lowercasing of variable names is consistently handled across both the configuration and API response.

existingVariables = existingVariables.filter(_var => _var.name !== variable.name)