Add notification channels and a provider abstraction

Users get a notification_channels table (replacing users.ntfy_topic); pages fan
out to every enabled channel through a notify.Provider registry, with ntfy as
the first provider. Fallbacks are typed {type, address}. Schema edited in place:
existing databases must be recreated.

Claude-Session: https://claude.ai/code/session_016mBLURvJoMuUEr9cB2RpUN

internal/api/notify_test.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"git.ryuvia.com/niklas/terdut-server/internal/api"
+	"git.ryuvia.com/niklas/terdut-server/internal/notify"
 )
 
 // ---------------------------------------------------------------------------
@@ -91,6 +92,15 @@ func (f *fakeNtfy) forget() {
 	f.got = nil
 }
 
+// providers registers the fake as the install's one ntfy provider.
+func (f *fakeNtfy) providers() *notify.Registry {
+	return notify.NewRegistry(notify.NewNtfy(f.URL, ""))
+}
+
+func ntfyTarget(topic string) notify.Target {
+	return notify.Target{Type: notify.TypeNtfy, Address: topic}
+}
+
 func (f *fakeNtfy) failWith(status int) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
@@ -106,11 +116,11 @@ func (f *fakeNtfy) failWith(status int) {
 func notifyTS(t *testing.T, cfg api.NotifyConfig) (*ts, *fakeNtfy) {
 	t.Helper()
 	f := newFakeNtfy(t)
-	cfg.BaseURL = f.URL
+	cfg.Providers = f.providers()
 	s := newTS(t, cfg)
 
 	putOnCall(t, s, 1)
-	setTopic(t, s, 1, "terdut-admin")
+	addNtfyChannel(t, s, 1, "terdut-admin")
 	return s, f
 }
 
@@ -125,13 +135,14 @@ func putOnCall(t *testing.T, s *ts, userID int) {
 	}
 }
 
-func setTopic(t *testing.T, s *ts, userID int, topic string) {
+// addNtfyChannel gives a user an ntfy channel, the way the Account page does.
+func addNtfyChannel(t *testing.T, s *ts, userID int, topic string) {
 	t.Helper()
-	resp := s.req(t, http.MethodPut,
-		fmt.Sprintf("/api/users/%d/notify", userID), map[string]any{"ntfy_topic": topic})
+	resp := s.req(t, http.MethodPost, fmt.Sprintf("/api/users/%d/channels", userID),
+		map[string]any{"type": "ntfy", "address": topic})
 	defer resp.Body.Close()
-	if resp.StatusCode != http.StatusOK {
-		t.Fatalf("set notify topic returned %d", resp.StatusCode)
+	if resp.StatusCode != http.StatusCreated {
+		t.Fatalf("add notification channel returned %d", resp.StatusCode)
 	}
 }
 
@@ -339,8 +350,8 @@ func TestNotify_DeliveryIsRecordedOnTheTimeline(t *testing.T) {
 	if e["type"] != "notified" {
 		t.Errorf("expected a notified event, got %v", e["type"])
 	}
-	if e["detail"] != "triggered" {
-		t.Errorf("expected the kind in detail, got %v", e["detail"])
+	if e["detail"] != "triggered via ntfy" {
+		t.Errorf("expected the kind and the channel type in detail, got %v", e["detail"])
 	}
 	if e["username"] != "admin" {
 		t.Errorf("expected the paged user attached, got %v", e["username"])
@@ -370,7 +381,7 @@ func TestNotify_TimelineRecordsOneEventPerDelivery(t *testing.T) {
 	if len(events) != 2 {
 		t.Fatalf("expected one event per delivery, got %v", events)
 	}
-	if events[0]["detail"] != "triggered" || events[1]["detail"] != "reminder" {
+	if events[0]["detail"] != "triggered via ntfy" || events[1]["detail"] != "reminder via ntfy" {
 		t.Errorf("expected triggered then reminder, got %v and %v",
 			events[0]["detail"], events[1]["detail"])
 	}
@@ -392,7 +403,7 @@ func TestNotify_AllClearIsRecordedOnTheTimeline(t *testing.T) {
 	if len(events) != 2 {
 		t.Fatalf("expected the all-clear recorded, got %v", events)
 	}
-	if events[1]["detail"] != "resolved" {
+	if events[1]["detail"] != "resolved via ntfy" {
 		t.Errorf("expected a resolved event, got %v", events[1]["detail"])
 	}
 }
@@ -402,9 +413,9 @@ func TestNotify_AllClearIsRecordedOnTheTimeline(t *testing.T) {
 func TestNotify_FallbackDeliveryHasNoUser(t *testing.T) {
 	f := newFakeNtfy(t)
 	s := newTS(t, api.NotifyConfig{
-		BaseURL:       f.URL,
-		FallbackTopic: "terdut-oncall",
-		PublicURL:     "https://terdut.example.com",
+		Providers: f.providers(),
+		Fallback:  ntfyTarget("terdut-oncall"),
+		PublicURL: "https://terdut.example.com",
 	})
 
 	fireCritical(t, s)
@@ -441,7 +452,7 @@ func TestNotify_ExhaustedRetriesAreRecordedOnce(t *testing.T) {
 		t.Errorf("expected notify_failed, got %v", events[0]["type"])
 	}
 	detail, _ := events[0]["detail"].(string)
-	if !strings.HasPrefix(detail, "triggered: ") || !strings.Contains(detail, "500") {
+	if !strings.HasPrefix(detail, "triggered via ntfy: ") || !strings.Contains(detail, "500") {
 		t.Errorf("expected the kind and the reason in %q", detail)
 	}
 }
@@ -743,12 +754,12 @@ func TestNotify_ManualResolveSendsNothing(t *testing.T) {
 
 // With nobody on call the page goes to the shared fallback, and carries no
 // Acknowledge button — there is no user to attribute the acknowledgement to.
-func TestNotify_FallbackTopicHasNoAckButton(t *testing.T) {
+func TestNotify_FallbackHasNoAckButton(t *testing.T) {
 	f := newFakeNtfy(t)
 	s := newTS(t, api.NotifyConfig{
-		BaseURL:       f.URL,
-		FallbackTopic: "terdut-oncall",
-		PublicURL:     "https://terdut.example.com",
+		Providers: f.providers(),
+		Fallback:  ntfyTarget("terdut-oncall"),
+		PublicURL: "https://terdut.example.com",
 	})
 
 	fireCritical(t, s)
@@ -770,7 +781,7 @@ func TestNotify_FallbackTopicHasNoAckButton(t *testing.T) {
 // only pile up rows that can never be delivered.
 func TestNotify_NoTargetQueuesNothing(t *testing.T) {
 	f := newFakeNtfy(t)
-	s := newTS(t, api.NotifyConfig{BaseURL: f.URL})
+	s := newTS(t, api.NotifyConfig{Providers: f.providers()})
 
 	fireCritical(t, s)
 
@@ -787,7 +798,9 @@ func TestNotify_NoTargetQueuesNothing(t *testing.T) {
 func TestNotify_DisabledQueuesNothing(t *testing.T) {
 	s := newTS(t)
 	putOnCall(t, s, 1)
-	setTopic(t, s, 1, "terdut-admin")
+	// Inserted rather than added through the API, which refuses a type this
+	// server has no provider for.
+	s.exec(t, "INSERT INTO notification_channels (user_id, type, address) VALUES (1, 'ntfy', 'terdut-admin')")
 
 	fireCritical(t, s)