Stage 4: TerdutAlertSource

Covers webhook Secret generation/ownership (DESIGN.md §4.5, §7), the
WebhookSecretLost fail-closed condition, and the kind-change
delete-and-recreate rotation path.

Idempotent-create here is deliberately neither adopt-on-409
(Team/service-account) nor list-and-match-by-name (TerdutDeadmanSwitch):
terdut-server shows the webhook key exactly once, at creation, and never
again, so no server-side lookup could ever recover it after a crash.
Instead the generated webhook Secret itself -- written immediately after
the POST, before status is ever touched -- is this CR's only durable
record that a create already succeeded; found with status.integrationID
still unset on a later reconcile, it's read back directly rather than
POSTing a second, orphaned integration. Found missing with
status.integrationID *set* instead, that's the already-designed
WebhookSecretLost case: fail closed, not self-healed, since the key is
genuinely gone and recreating it would rotate a live webhook URL with no
spec change to explain why.

Renaming (PATCH) never touches the key, so it's applied unconditionally
every reconcile, same as the escalation policy's whole-policy PUT. A
spec.kind change is the one case with no in-place update verb at all:
DELETE the old integration, delete the stale webhook Secret, then run the
same create path fresh -- fires a Warning event since this breaks whatever
still sends to the old URL.

Also: fakeTerdutServer grows POST/PATCH/DELETE .../integrations routes
behind a new handleIntegrationSubPath, split out of handleTeamSubPath to
stay under gocyclo's threshold; three goconst-flagged test literals
("does-not-exist", "unready") and one unparam-flagged test helper
parameter (bootstrapReadyTerdutServer's always-"default" namespace) get
shared/removed now that a fourth same-shaped caller made the repetition
concrete enough for the linter to flag.

DESIGN.md §13 gains one honest gap found while grounding this stage, not
introduced by it: no child CRD specially detects a mid-life teamRef
change; all three always resolve spec.teamRef fresh and trust the
already-stored server-side id remains valid there.

make fmt lint test build all clean; internal/controller envtest coverage
holds at 71.6%.

config/samples/kustomization.yaml

@@ -4,4 +4,5 @@ resources:
 - terdut_v1alpha1_terdutteam.yaml
 - terdut_v1alpha1_terdutescalationrule.yaml
 - terdut_v1alpha1_terdutdeadmanswitch.yaml
+- terdut_v1alpha1_terdutalertsource.yaml
 # +kubebuilder:scaffold:manifestskustomizesamples

config/samples/terdut_v1alpha1_terdutalertsource.yaml

@@ -0,0 +1,19 @@
+apiVersion: terdut.ryuvia.com/v1alpha1
+kind: TerdutAlertSource
+metadata:
+  labels:
+    app.kubernetes.io/name: terdut-operator
+    app.kubernetes.io/managed-by: kustomize
+  name: terdutalertsource-sample
+spec:
+  teamRef:
+    name: terdutteam-sample
+  # kind defaults to "alertmanager" -- the only value terdut-server
+  # supports today. Changing it after this object exists rotates the
+  # webhook key (DESIGN.md §5): the old integration is deleted and a new
+  # one created, which breaks whatever still sends to the old URL.
+  kind: alertmanager
+  # name is this source's own display name server-side, distinct from this
+  # object's own metadata.name above -- renaming it is safe and never
+  # rotates the key.
+  name: prod-alertmanager