Prevent Nightwatch middleware from being registered multiple times

[dwjordan]

Summary

When the Nightwatch middleware is added to a connector that is reused across multiple requests, the middleware is registered repeatedly on subsequent requests. This results in duplicate middleware execution and inflated Nightwatch metrics.

Problem

The Nightwatch plugin registers its middleware via addMiddleware on the Guzzle handlerStack, which does not de-duplicate entries. When a Connector instance is reused, the Nightwatch middleware is appended again on each request, causing the middleware to run multiple times per request lifecycle.

Because Nightwatch is intended to observe outgoing requests once per execution, this leads to significant oversampling.

Fix

Before registering the Nightwatch middleware, remove any existing middleware tagged as nightwatch from the handler stack. This ensures the middleware is only applied once, even when connectors are reused.

Tests

• Added a regression test that reproduces the middleware duplication when reusing a connector.
• The test fails on main and passes with this change.
• Verified that the Nightwatch middleware executes only once per request across multiple uses of the same connector instance.

[JonPurvis]

Thanks @dwjordan, this makes sense.

Please could you run ./vendor/bin/php-cs-fixer fix --allow-risky=yes and push the change(s) up? That action only runs if Sam does it!

[JonPurvis]

Speedy! 🚀

Thanks! I've got a call with Sam later tonight so we'll go through this PR

[dwjordan]

Sounds good, thanks!

[Sammyjo20]

Fantastic PR thanks @dwjordan and @JonPurvis for pairing! 🍐