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; a blank field on the add target form gives 1, and on the
edit form keeps the stored value. 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/handlers/target_create_test.go

@@ -21,24 +21,24 @@ func TestHandleTargetCreate_EveryType(t *testing.T) {
 
 	// fields is the rest of each submission, as a query string.
 	cases := []struct {
-		targetType  database.TargetType
-		fields      string
-		wantConfig  string
-		wantRetries int
+		targetType   database.TargetType
+		fields       string
+		wantConfig   string
+		wantAttempts int
 	}{
 		{
-			database.TargetTypeHTTP, "timeout=12&max_retries=3",
+			database.TargetTypeHTTP, "timeout=12&max_attempts=3",
 			`{"url":"` + editOriginalURL + `","timeout":12}`, 3,
 		},
 		{
-			database.TargetTypeSlack, "max_retries=4",
+			database.TargetTypeSlack, "max_attempts=4",
 			`{"webhookUrl":"` + editOriginalURL + `"}`, 4,
 		},
 		{
 			database.TargetTypeDatabase, "expiry=720h",
-			`{"expiry":"720h"}`, 0,
+			`{"expiry":"720h"}`, 1,
 		},
-		{database.TargetTypeLog, "", "", 0},
+		{database.TargetTypeLog, "", "", 1},
 	}
 
 	for _, tc := range cases {
@@ -62,7 +62,7 @@ func TestHandleTargetCreate_EveryType(t *testing.T) {
 			targets := targetsForWebhook(t, env.db, webhook.ID)
 			require.Len(t, targets, 1)
 			assert.Equal(t, tc.targetType, targets[0].Type)
-			assert.Equal(t, tc.wantRetries, targets[0].MaxRetries)
+			assert.Equal(t, tc.wantAttempts, targets[0].MaxAttempts)
 
 			if tc.wantConfig == "" {
 				assert.Empty(t, targets[0].Config)
@@ -90,11 +90,11 @@ func TestHandleTargetCreate_RefusedFormComesBack(t *testing.T) {
 		{
 			database.TargetTypeHTTP,
 			"name=private&url=" + editBlockedURL +
-				"&timeout=12&max_retries=3",
+				"&timeout=12&max_attempts=3",
 			"Invalid target URL",
 		},
 		{
-			database.TargetTypeSlack, "name=no-url&max_retries=4",
+			database.TargetTypeSlack, "name=no-url&max_attempts=4",
 			"Webhook URL is required for Slack targets",
 		},
 		{
@@ -133,8 +133,8 @@ func TestHandleTargetCreate_RefusedFormComesBack(t *testing.T) {
 			assert.Contains(t, page, html.EscapeString(tc.reason))
 
 			// Each value comes back in a data attribute of the targets
-			// section named after its field (max_retries as
-			// data-max-retries), except url, which comes back in
+			// section named after its field (max_attempts as
+			// data-max-attempts), except url, which comes back in
 			// data-destination; templates/source_detail.html says why.
 			for field := range typed {
 				attr := "data-" + strings.ReplaceAll(field, "_", "-")