net: unify testing certificates infra

[MustafaSaber]

Currently testing cert infra is scattered across the repo

mTLS, oauthGrant, proxy and next would be swarm TLS. This is an attempt to unify before we have more uses cases

related to #4328

• All old tests should be passing

[zalando-robot]

Docker image "registry-write.opensource.zalan.do/teapot/skipper:5e11a12cd41c670647f339484db33467b1f52a3b" is not based on an approved base image. Any production deployment relying on this image will be blocked.

To create a compliant Docker image of your application, you must reference an allowed Docker image as its base image in your Dockerfile. This base image must come from the Zalando Container Registry namespace library and use a recommended version as listed in the documentation.

[zalando-robot]

Docker image "registry-write.opensource.zalan.do/teapot/skipper:2d6fd1a7df6f37a38d558939897a670a173a45e4" is not based on an approved base image. Any production deployment relying on this image will be blocked.

To create a compliant Docker image of your application, you must reference an allowed Docker image as its base image in your Dockerfile. This base image must come from the Zalando Container Registry namespace library and use a recommended version as listed in the documentation.

[zalando-robot]

Docker image "registry-write.opensource.zalan.do/teapot/skipper:d4d79b6cbc86a6d866e964eee614a165f17d38c3" is not based on an approved base image. Any production deployment relying on this image will be blocked.

To create a compliant Docker image of your application, you must reference an allowed Docker image as its base image in your Dockerfile. This base image must come from the Zalando Container Registry namespace library and use a recommended version as listed in the documentation.

[MustafaSaber]

👍