Store a target's number of delivery attempts, at least one (closes #540)

Target.MaxRetries (max_retries) becomes Target.MaxAttempts
(max_attempts), and the form field, parser and ceiling are renamed to
match. 1 is a single attempt with no circuit breaker; above 1 retries
behind the breaker up to that many attempts. Both target forms refuse
0 and less and default a blank field to 1. The target page shows the
plain number, and the README's two paragraphs on 0 against 1 become
one sentence.

Model: opus-5-5

internal/delivery/target_config_view_test.go

@@ -32,7 +32,7 @@ const (
 	viewMaskedOrigin  = viewExampleOrigin + "/..."
 	viewUnavailable   = "(unavailable)"
 	viewExpiryNever   = "never"
-	viewMaxRetries    = "Delivery attempts"
+	viewMaxAttempts   = "Delivery attempts"
 )
 
 func TestMaskedWebhookURL(t *testing.T) {
@@ -171,6 +171,7 @@ func slackTarget() database.Target {
 		Active: true,
 		Config: `{"webhookUrl":"` +
 			slackWebhookURL + `"}`,
+		MaxAttempts: 1,
 	}
 }
 
@@ -189,28 +190,29 @@ func TestNewTargetViews_Slack(t *testing.T) {
 	assert.Equal(
 		t,
 		map[string]string{
-			"Webhook URL":  slackMaskedURL,
-			viewMaxRetries: "1 (fire-and-forget: no retries, no circuit breaker)",
+			"Webhook URL":   slackMaskedURL,
+			viewMaxAttempts: "1",
 		},
 		fieldMap(view.Config),
 	)
 }
 
-// TestNewTargetViews_SlackRetries proves a Slack target shows
-// its retry count the same way an HTTP target does.
-func TestNewTargetViews_SlackRetries(t *testing.T) {
+// TestNewTargetViews_SlackAttempts proves a Slack target shows
+// its number of delivery attempts the same way an HTTP target
+// does.
+func TestNewTargetViews_SlackAttempts(t *testing.T) {
 	t.Parallel()
 
 	target := slackTarget()
-	target.MaxRetries = 2
+	target.MaxAttempts = 2
 
 	view := viewFor(t, target)
 
 	assert.Equal(
 		t,
 		map[string]string{
-			"Webhook URL":  slackMaskedURL,
-			viewMaxRetries: "2",
+			"Webhook URL":   slackMaskedURL,
+			viewMaxAttempts: "2",
 		},
 		fieldMap(view.Config),
 	)
@@ -225,7 +227,7 @@ func TestNewTargetViews_HTTP(t *testing.T) {
 			`"timeout":30,` +
 			`"headers":{"Authorization":"Bearer sekrit"},` +
 			`"forwardQuery":true}`,
-		MaxRetries: 5,
+		MaxAttempts: 5,
 	})
 
 	fields := fieldMap(view.Config)
@@ -237,7 +239,7 @@ func TestNewTargetViews_HTTP(t *testing.T) {
 			"Timeout":         "30s",
 			"Headers":         "1 configured",
 			"Query string":    "passed on to this target",
-			viewMaxRetries:    "5",
+			viewMaxAttempts:   "5",
 		},
 		fields,
 	)
@@ -248,19 +250,22 @@ func TestNewTargetViews_HTTP(t *testing.T) {
 	}
 }
 
-func TestNewTargetViews_HTTPFireAndForget(t *testing.T) {
+// TestNewTargetViews_HTTPSingleAttempt proves a single attempt is
+// shown as the plain number, like any other.
+func TestNewTargetViews_HTTPSingleAttempt(t *testing.T) {
 	t.Parallel()
 
 	view := viewFor(t, database.Target{
-		Type:   database.TargetTypeHTTP,
-		Config: `{"url":"` + viewExampleHook + `"}`,
+		Type:        database.TargetTypeHTTP,
+		Config:      `{"url":"` + viewExampleHook + `"}`,
+		MaxAttempts: 1,
 	})
 
 	assert.Equal(
 		t,
 		map[string]string{
 			"Destination URL": viewMaskedOrigin,
-			viewMaxRetries:    "1 (fire-and-forget: no retries, no circuit breaker)",
+			viewMaxAttempts:   "1",
 		},
 		fieldMap(view.Config),
 	)