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

A database target's rotation (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, the add target form and the target edit form, and shown in the
target list.

Renames move every one of a target's files, the sweep prunes every file
and deletes a rotated file it leaves empty, Download exports every file
oldest first with each row's period, and the target list names the
current file and totals the size of all of them.

Model: opus-5-5

internal/handlers/handlers_test.go

@@ -436,23 +436,37 @@ 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(
@@ -461,7 +475,7 @@ 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(
@@ -471,3 +485,20 @@ 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)
+	}
+}