feat: writing logs to the filesystem with rotation support (#1299)

* refactor: move lib/policy/config to lib/config

Signed-off-by: Xe Iaso <me@xeiaso.net>

* refactor: don't set global loggers anymore

Ref #864

You were right @kotx, it is a bad idea to set the global logger
instance.

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(config): add log sink support

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: update spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(test): go mod tidy

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: update spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs(admin/policies): add logging block documentation

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs: update CHANGELOG

Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix(cmd/anubis): revert this change, it's meant to be its own PR

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: go mod tidy

Signed-off-by: Xe Iaso <me@xeiaso.net>

* test: add file logging smoke test

Assisted-by: GLM 4.6 via Claude Code
Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix: don't expose the old log file time format string

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/config/impressum.go

@@ -0,0 +1,71 @@
+package config
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+)
+
+var ErrMissingValue = errors.New("config: missing value")
+
+type Impressum struct {
+	Footer string        `json:"footer" yaml:"footer"`
+	Page   ImpressumPage `json:"page" yaml:"page"`
+}
+
+func (i Impressum) Render(_ context.Context, w io.Writer) error {
+	if _, err := fmt.Fprint(w, i.Footer); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (i Impressum) Valid() error {
+	var errs []error
+
+	if len(i.Footer) == 0 {
+		errs = append(errs, fmt.Errorf("%w: impressum footer must be defined", ErrMissingValue))
+	}
+
+	if err := i.Page.Valid(); err != nil {
+		errs = append(errs, err)
+	}
+
+	if len(errs) != 0 {
+		return errors.Join(errs...)
+	}
+
+	return nil
+}
+
+type ImpressumPage struct {
+	Title string `json:"title" yaml:"title"`
+	Body  string `json:"body" yaml:"body"`
+}
+
+func (ip ImpressumPage) Render(_ context.Context, w io.Writer) error {
+	if _, err := fmt.Fprint(w, ip.Body); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (ip ImpressumPage) Valid() error {
+	var errs []error
+
+	if len(ip.Title) == 0 {
+		errs = append(errs, fmt.Errorf("%w: impressum page title must be defined", ErrMissingValue))
+	}
+
+	if len(ip.Body) == 0 {
+		errs = append(errs, fmt.Errorf("%w: impressum body title must be defined", ErrMissingValue))
+	}
+
+	if len(errs) != 0 {
+		return errors.Join(errs...)
+	}
+
+	return nil
+}