NO-JIRA: chore(docs/adr): document onboarding onto all possible test execution platforms for evaluation (#2627)

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

Author: jiridanek

docs/architecture/decisions/0002-onboard-onto-all-possible-test-execution-platforms-available.md

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+# 2. Onboard onto all possible test execution platforms available
+
+Date: 2025-10-29
+
+## Status
+
+Accepted
+
+## Context
+
+We as the Notebooks team need to be responsible for the test execution on our code.
+To do that, we need to explore options available and decide which ones to use.
+
+## Decision
+
+We will onboard and create some quick-start-style tests on all platforms available to us.
+This will provide us with sufficient knowledge to talk to Red Hat DevTestOps team on equal footing about what we actually need.
+
+### Execution platforms to consider for onboarding
+
+* OpenShift CI (already onboarded)
+* GitHub Actions (already onboarded)
+* Konflux [E2E test execution](https://developers.redhat.com/articles/2024/10/28/ephemeral-openshift-clusters-konflux-ci-using-cluster-service-operator)
+* Travis CI Partner Queue
+* Packit.dev
+* Testing-Farm.io nested virtualization
+* <https://github.com/jiridanek/rhoai-in-kind>
+* Hydra trigger such as /test-e2e that will run something on Red Hat internal CI
+* Machine under @jiridanek's desk in Brno
+* Virtual machines under our management on ITUP.scale platform in Red Hat
+
+## Consequences
+
+This is related to [E2E Testing Platform Evaluation - Periodic Review #1389](https://github.com/opendatahub-io/notebooks/issues/1389).
+
+We'll need to maintain the test execution platforms we choose to use.
+We'll need to eventually offboard from the platforms we decide not to use, to avoid confusion.