BitbucketServer Webhooks: diagnostic:ping not working after upgrade to v2.0.0

[mhoyer]

Checklist:

• I've searched in the docs and FAQ for my answer: https://bit.ly/argocd-faq.
• I've included steps to reproduce the bug.
• I've pasted the output of argocd version.

Describe the bug

With the previous installation of ArgoCD v1.8.7 (and earlier) we successfully established a webhook with our own on-premise Bitbucket server (currently v7.10.1) following the guidelines in the docs. After the update to v2.0.0 last week it's still working, but started to break with diagnostic:ping events.

In Bitbucket the Test connection button now fails with a 400:

The Webhook event details ("View details") show me:

Request details

Headers

X-Event-Key: diagnostics:ping
X-Request-Id: a528e9e3-d16f-4746-8772-91d58192d7bd
Content-Type: application/json

Body

{"test": true}

Response

HTTP status: 200

Headers

Connection: keep-alive
Content-Length: 58
X-Content-Type-Options: nosniff
Date: Tue, 13 Apr 2021 16:31:58 GMT
Via: 1.1 localhost (Apache-HttpClient/4.5.5 (cache))
Content-Type: text/plain; charset=UTF-8

Body

Webhook processing failed: event not defined to be parsed

... and in the logs of the argocd-server pod I find similar lines related to the "test connection" requests:

time="2021-04-13T15:56:26Z" level=info msg="Webhook processing failed: event not defined to be parsed"

I guess this is simply and straight related to #5565, which actually enabled the exposure of such a errors at all!? Still it's weird. Hence, the underlying go-playground/webhooks repository knows about this diagnostics:ping event: bitbucket-server/bitbucketserver.go#L51.

To Reproduce

Just POST this request to the Argo CD webhook endpoint:

POST /api/webhook
X-Event-Key: diagnostics:ping
X-Request-Id: a528e9e3-d16f-4746-8772-91d58192d7bd
Content-Type: application/json

{"test": true}

Expected behavior

• diagnostic:ping should work and return a 200 in Bitbucket server

Version

$ argocd version --port-forward --insecure
argocd: v2.0.0+f5119c0
  BuildDate: 2021-04-07T06:03:59Z
  GitCommit: f5119c06686399134b3f296d44445bcdbc778d42
  GitTreeState: clean
  GoVersion: go1.16
  Compiler: gc
  Platform: windows/amd64
argocd-server: v2.0.0+f5119c0
  BuildDate: 2021-04-07T06:00:33Z
  GitCommit: f5119c06686399134b3f296d44445bcdbc778d42
  GitTreeState: clean
  GoVersion: go1.16
  Compiler: gc
  Platform: linux/amd64
  Ksonnet Version: v0.13.1
  Kustomize Version: v3.9.4 2021-02-09T19:22:10Z
  Helm Version: v3.5.1+g32c2223
  Kubectl Version: v0.20.4
  Jsonnet Version: v0.17.0

Logs

Essential parts posted above already.