This PR fixes the `x-trigger-branch` header support for targeting specific preview branches when managing environment variables. The header was documented but not actually being extracted or used in the environment variable API routes. Additionally, the query logic in `authenticatedEnvironmentForAuthentication` was fundamentally broken—it searched for environments with both `slug: "preview"` (parent environment property) AND a specific `branchName` (child environment property), which no environment could satisfy simultaneously. The fix extracts the branch name using `branchNameFromRequest()` and correctly queries for child branch environments using `type: "PREVIEW"` and the specific `branchName`. This ensures that environment variable operations (create, update, get, list) properly target individual preview branches instead of affecting all preview environments.
Eric Allam
4347499799