Load every setting from one table in internal/config (closes #320)

Config.settings lists each setting once: its key, its environment
variable and the function that loads it. Most rows load through field,
whose arguments give the type, the default and the check. db_url and
cache_max_bytes keep their own load functions. Loading, the unknown-key
and unknown-variable checks and the names in error messages all read
the table. allowlist_hosts now loads through parseHostList, as
referer_blocklist does. isKnownConfigKey, envVarNames, strictLoader,
validate, validateAllowlistHostsValue and getStringSlice are gone, with
the getStringSlice tests. The key constants move to the tests, their
only users. A new test checks that README.md and
configs/config.example.yml name the keys of the table.

Model: opus-5-5

internal/config/config_internal_test.go

@@ -1,97 +1,12 @@
 package config
 
 import (
-	"os"
 	"path/filepath"
 	"testing"
 
 	"git.eeqj.de/sneak/smartconfig"
 )
 
-// writeTestConfig writes yamlContent to a temp config file and returns
-// the file path.
-func writeTestConfig(t *testing.T, yamlContent string) string {
-	t.Helper()
-
-	tmpDir := t.TempDir()
-	configPath := filepath.Join(tmpDir, "config.yml")
-
-	err := os.WriteFile(configPath, []byte(yamlContent), 0o600)
-	if err != nil {
-		t.Fatalf("failed to write test config: %v", err)
-	}
-
-	return configPath
-}
-
-// checkAllowlistHosts loads the config at configPath and asserts that
-// getStringSlice returns the three expected hosts.
-func checkAllowlistHosts(t *testing.T, configPath string) {
-	t.Helper()
-
-	sc, err := loadTestConfig(configPath)
-	if err != nil {
-		t.Fatalf("failed to load config: %v", err)
-	}
-
-	hosts := getStringSlice(sc)
-
-	if len(hosts) != 3 {
-		t.Errorf("expected 3 hosts, got %d: %v", len(hosts), hosts)
-	}
-
-	expected := []string{"static.sneak.cloud", "sneak.berlin", testHostS3}
-	for i, want := range expected {
-		if i >= len(hosts) {
-			t.Errorf("missing host at index %d: want %q", i, want)
-
-			continue
-		}
-
-		if hosts[i] != want {
-			t.Errorf("host[%d] = %q, want %q", i, hosts[i], want)
-		}
-	}
-}
-
-func TestGetStringSlice_YAMLList(t *testing.T) {
-	t.Parallel()
-
-	yamlContent := `
-allowlist_hosts:
-  - static.sneak.cloud
-  - sneak.berlin
-  - s3.sneak.cloud
-`
-
-	checkAllowlistHosts(t, writeTestConfig(t, yamlContent))
-}
-
-func TestGetStringSlice_CommaSeparated(t *testing.T) {
-	t.Parallel()
-
-	// Backwards compatibility with comma-separated string values.
-	yamlContent := `allowlist_hosts: "static.sneak.cloud, sneak.berlin, s3.sneak.cloud"`
-
-	checkAllowlistHosts(t, writeTestConfig(t, yamlContent))
-}
-
-func TestGetStringSlice_Empty(t *testing.T) {
-	t.Parallel()
-
-	configPath := writeTestConfig(t, `port: 8080`)
-
-	sc, err := loadTestConfig(configPath)
-	if err != nil {
-		t.Fatalf("failed to load config: %v", err)
-	}
-
-	hosts := getStringSlice(sc)
-	if len(hosts) != 0 {
-		t.Errorf("expected nil or empty slice, got %v", hosts)
-	}
-}
-
 // TestExampleConfigAllowlistsNoHost loads configs/config.example.yml
 // with a real signing key, as Getting Started in README.md has it copied
 // and edited, and checks that it allowlists no host: every image on an