Rotate a database target's archive monthly, daily or hourly (closes #379)

A database target's rotation setting (none, monthly, daily or hourly) puts the UTC period of each event's receive time in its archive file name, so each file holds exactly its period's events. It is on the new webhook page and both target forms, and shown in the target list. Renames move every one of a target's files and move them all back if one fails. The sweep prunes one file at a time under the target's lock and deletes a rotated file it leaves empty. Download opens one file at a time, oldest period first, finding each again under the target's current name. The target list names the current file and totals all of them.

Model: opus-5-5

internal/handlers/handlers_test.go

@@ -477,23 +477,37 @@ func TestRenderTemplateMidRenderErrorSendsNoPartialBody(t *testing.T) {
 func TestBuildDatabaseTargetConfig_Valid(t *testing.T) {
 	t.Parallel()
 
-	// Empty expiry: the keep-forever default, empty config.
-	cfg, errMsg, err := handlers.BuildDatabaseTargetConfigForTest("")
+	// Empty expiry and rotation: the keep-forever, one-file default,
+	// empty config.
+	cfg, errMsg, err := handlers.BuildDatabaseTargetConfigForTest("", "")
 	require.NoError(t, err)
 	assert.Empty(t, errMsg)
 	assert.Empty(t, cfg)
 
 	// Explicit never is stored as config.
-	cfg, errMsg, err = handlers.BuildDatabaseTargetConfigForTest("never")
+	cfg, errMsg, err = handlers.BuildDatabaseTargetConfigForTest("never", "")
 	require.NoError(t, err)
 	assert.Empty(t, errMsg)
 	assert.JSONEq(t, `{"expiry":"never"}`, cfg)
 
 	// A positive duration is stored as config.
-	cfg, errMsg, err = handlers.BuildDatabaseTargetConfigForTest("720h")
+	cfg, errMsg, err = handlers.BuildDatabaseTargetConfigForTest("720h", "")
 	require.NoError(t, err)
 	assert.Empty(t, errMsg)
 	assert.JSONEq(t, `{"expiry":"720h"}`, cfg)
+
+	// A rotation is stored as config, with or without an expiry.
+	cfg, errMsg, err = handlers.BuildDatabaseTargetConfigForTest("", "daily")
+	require.NoError(t, err)
+	assert.Empty(t, errMsg)
+	assert.JSONEq(t, `{"rotation":"daily"}`, cfg)
+
+	cfg, errMsg, err = handlers.BuildDatabaseTargetConfigForTest(
+		"720h", "hourly",
+	)
+	require.NoError(t, err)
+	assert.Empty(t, errMsg)
+	assert.JSONEq(t, `{"expiry":"720h","rotation":"hourly"}`, cfg)
 }
 
 func TestBuildDatabaseTargetConfig_RejectsBadExpiry(
@@ -502,7 +516,7 @@ func TestBuildDatabaseTargetConfig_RejectsBadExpiry(
 	t.Parallel()
 
 	for _, bad := range []string{"nonsense", "7d", "-5h"} {
-		cfg, errMsg, err := handlers.BuildDatabaseTargetConfigForTest(bad)
+		cfg, errMsg, err := handlers.BuildDatabaseTargetConfigForTest(bad, "")
 
 		require.NoError(t, err)
 		assert.Contains(
@@ -512,3 +526,20 @@ func TestBuildDatabaseTargetConfig_RejectsBadExpiry(
 		assert.Empty(t, cfg)
 	}
 }
+
+func TestBuildDatabaseTargetConfig_RejectsBadRotation(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	for _, bad := range []string{"weekly", "Daily", " none"} {
+		cfg, errMsg, err := handlers.BuildDatabaseTargetConfigForTest("", bad)
+
+		require.NoError(t, err)
+		assert.Contains(
+			t, errMsg, "Invalid archive rotation",
+			"rotation %q should be refused", bad,
+		)
+		assert.Empty(t, cfg)
+	}
+}