Increase fetch interval for Codeberg

Increase the fetch interval to at least 30 seconds if the runner is
configured to be used with Codeberg. This avoids it being rate limited
when they do actual work and reduces load on Codeberg.

internal/pkg/config/config_test.go

@@ -0,0 +1,37 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package config
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestConfigTune(t *testing.T) {
+	c := &Config{
+		Runner: Runner{},
+	}
+
+	t.Run("Public instance tuning", func(t *testing.T) {
+		c.Runner.FetchInterval = 60 * time.Second
+		c.Tune("https://codeberg.org")
+		assert.EqualValues(t, 60*time.Second, c.Runner.FetchInterval)
+
+		c.Runner.FetchInterval = 2 * time.Second
+		c.Tune("https://codeberg.org")
+		assert.EqualValues(t, 30*time.Second, c.Runner.FetchInterval)
+	})
+
+	t.Run("Non-public instance tuning", func(t *testing.T) {
+		c.Runner.FetchInterval = 60 * time.Second
+		c.Tune("https://example.com")
+		assert.EqualValues(t, 60*time.Second, c.Runner.FetchInterval)
+
+		c.Runner.FetchInterval = 2 * time.Second
+		c.Tune("https://codeberg.com")
+		assert.EqualValues(t, 2*time.Second, c.Runner.FetchInterval)
+	})
+}