chore: replace bunyan-middleware

[Trott]

bunyan-middleware has not had an update for four years in either its GitHub repo or its npm version. It is tiny and easy to replicate without dependencies, so let's do that.

[Copilot]

Pull request overview

This PR replaces the unmaintained bunyan-middleware dependency with an in-repo request logging middleware that attaches request-scoped Bunyan child loggers and obscures the GitHub webhook signature in serialized request headers.

Changes:

• Remove bunyan-middleware from dependencies and wire up a new local requestLogger middleware in app.js.
• Add lib/request-logger.js to generate/propagate request IDs and emit a trace log on response finish with request/response serializers.
• Add a unit test validating request logger attachment and header obscuring behavior.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
app.js	Replaces bunyan-middleware usage with the new local request logger middleware.
lib/request-logger.js	Implements request-scoped logging, request-id propagation, and header obscuring in serializers.
test/unit/request-logger.test.js	Adds unit coverage for request logger behavior (request id propagation and finish logging).
package.json	Removes the bunyan-middleware dependency.
package-lock.json	Removes bunyan-middleware and updates lockfile resolution metadata / transitive versions.

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