Hi… I am well aware that this diff view is very suboptimal. It will be fixed when the refactored server comes along!
Add HTTP 451
// SPDX-License-Identifier: AGPL-3.0-only
// SPDX-FileContributor: Runxi Yu <https://runxiyu.org>
package main
import (
	"net/http"
)
func errorPage404(w http.ResponseWriter, params map[string]any) {
	w.WriteHeader(404)
	_ = templates.ExecuteTemplate(w, "404", params)
}
func errorPage400(w http.ResponseWriter, params map[string]any, msg string) {
	w.WriteHeader(400)
params["bad_request_msg"] = msg
params["complete_error_msg"] = msg
_ = templates.ExecuteTemplate(w, "400", params) }
func errorPage451(w http.ResponseWriter, params map[string]any, msg string) {
	w.WriteHeader(451)
	params["complete_error_msg"] = msg
	_ = templates.ExecuteTemplate(w, "451", params)
}
{{/*
	SPDX-License-Identifier: AGPL-3.0-only
	SPDX-FileContributor: Runxi Yu <https://runxiyu.org>
*/}}
{{- define "400" -}}
<!DOCTYPE html>
<html lang="en">
	<head>
		{{- template "head_common" . -}}
		<title>400 Bad Request – {{ .global.forge_title }}</title>
	</head>
	<body class="400">
		{{- template "header" . -}}
		<div class="padding-wrapper complete-error-page">
			<h1>400 Bad Request</h1>
			<p>{{- .bad_request_msg -}}</p>
			<p>{{- .complete_error_msg -}}</p>
			<hr />
			<address>Lindenii Forge</address>
		</div>
		<footer>
			{{- template "footer" . -}}
		</footer>
	</body>
</html>
{{- end -}}
{{/*
	SPDX-License-Identifier: AGPL-3.0-only
	SPDX-FileContributor: Runxi Yu <https://runxiyu.org>
*/}}
{{- define "451" -}}
<!DOCTYPE html>
<html lang="en">
	<head>
		{{- template "head_common" . -}}
		<title>451 Unavailable For Legal Reasons – {{ .global.forge_title }}</title>
	</head>
	<body class="451">
		{{- template "header" . -}}
		<div class="padding-wrapper complete-error-page">
			<h1>451 Unavailable For Legal Reasons</h1>
			<p>{{- .complete_error_msg -}}</p>
			<hr />
			<address>Lindenii Forge</address>
		</div>
		<footer>
			{{- template "footer" . -}}
		</footer>
	</body>
</html>
{{- end -}}