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%.

api/v1alpha1/zz_generated.deepcopy.go

@@ -135,6 +135,21 @@ func (in *ImageSpec) DeepCopy() *ImageSpec {
 	return out
 }
 
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *LocalSecretRef) DeepCopyInto(out *LocalSecretRef) {
+	*out = *in
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new LocalSecretRef.
+func (in *LocalSecretRef) DeepCopy() *LocalSecretRef {
+	if in == nil {
+		return nil
+	}
+	out := new(LocalSecretRef)
+	in.DeepCopyInto(out)
+	return out
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *NetworkingSpec) DeepCopyInto(out *NetworkingSpec) {
 	*out = *in
@@ -240,6 +255,108 @@ func (in *SweeperSpec) DeepCopy() *SweeperSpec {
 	return out
 }
 
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *TerdutAlertSource) DeepCopyInto(out *TerdutAlertSource) {
+	*out = *in
+	out.TypeMeta = in.TypeMeta
+	in.ObjectMeta.DeepCopyInto(&out.ObjectMeta)
+	out.Spec = in.Spec
+	in.Status.DeepCopyInto(&out.Status)
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new TerdutAlertSource.
+func (in *TerdutAlertSource) DeepCopy() *TerdutAlertSource {
+	if in == nil {
+		return nil
+	}
+	out := new(TerdutAlertSource)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
+func (in *TerdutAlertSource) DeepCopyObject() runtime.Object {
+	if c := in.DeepCopy(); c != nil {
+		return c
+	}
+	return nil
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *TerdutAlertSourceList) DeepCopyInto(out *TerdutAlertSourceList) {
+	*out = *in
+	out.TypeMeta = in.TypeMeta
+	in.ListMeta.DeepCopyInto(&out.ListMeta)
+	if in.Items != nil {
+		in, out := &in.Items, &out.Items
+		*out = make([]TerdutAlertSource, len(*in))
+		for i := range *in {
+			(*in)[i].DeepCopyInto(&(*out)[i])
+		}
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new TerdutAlertSourceList.
+func (in *TerdutAlertSourceList) DeepCopy() *TerdutAlertSourceList {
+	if in == nil {
+		return nil
+	}
+	out := new(TerdutAlertSourceList)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
+func (in *TerdutAlertSourceList) DeepCopyObject() runtime.Object {
+	if c := in.DeepCopy(); c != nil {
+		return c
+	}
+	return nil
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *TerdutAlertSourceSpec) DeepCopyInto(out *TerdutAlertSourceSpec) {
+	*out = *in
+	out.TeamRef = in.TeamRef
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new TerdutAlertSourceSpec.
+func (in *TerdutAlertSourceSpec) DeepCopy() *TerdutAlertSourceSpec {
+	if in == nil {
+		return nil
+	}
+	out := new(TerdutAlertSourceSpec)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *TerdutAlertSourceStatus) DeepCopyInto(out *TerdutAlertSourceStatus) {
+	*out = *in
+	if in.Conditions != nil {
+		in, out := &in.Conditions, &out.Conditions
+		*out = make([]v1.Condition, len(*in))
+		for i := range *in {
+			(*in)[i].DeepCopyInto(&(*out)[i])
+		}
+	}
+	if in.WebhookURLSecretRef != nil {
+		in, out := &in.WebhookURLSecretRef, &out.WebhookURLSecretRef
+		*out = new(LocalSecretRef)
+		**out = **in
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new TerdutAlertSourceStatus.
+func (in *TerdutAlertSourceStatus) DeepCopy() *TerdutAlertSourceStatus {
+	if in == nil {
+		return nil
+	}
+	out := new(TerdutAlertSourceStatus)
+	in.DeepCopyInto(out)
+	return out
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *TerdutDeadmanSwitch) DeepCopyInto(out *TerdutDeadmanSwitch) {
 	*out = *in