[feature] Public list of suspended domains (#1362)

* basic rendered domain blocklist (unauthenticated!)

* style basic domain block list

* better formatting for domain blocklist

* add opt-in config option for showing suspended domains

* format/linter

* re-use InstancePeersGet for web-accessible domain blocklist

* reword explanation, border styling

* always attach blocklist handler, update error message

* domain blocklist error message grammar

web/template/domain-blocklist.tmpl

@@ -0,0 +1,51 @@
+{{- /*
+	GoToSocial
+	Copyright (C) 2021-2023 GoToSocial Authors admin@gotosocial.org
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Affero General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU Affero General Public License for more details.
+
+	You should have received a copy of the GNU Affero General Public License
+	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/ -}}
+
+{{ template "header.tmpl" .}}
+<main>
+	<section>
+		<h1>Suspended Instances</h1>
+		<p>
+			The following list of domains have been suspended by the administrator(s) of this server.
+		</p>
+		<p>
+			All current and future accounts on these instances are blocked, and no more data is federated to the remote
+			servers.
+			This extends to subdomains, so an entry for 'example.com' includes 'social.example.com' as well.
+		</p>
+		<div class="list domain-blocklist">
+			<div class="header entry">
+				<div class="domain">Domain</div>
+				<div class="public_comment">Public comment</div>
+			</div>
+			{{range .blocklist}}
+			<div class="entry" id="{{.Domain}}">
+				<div class="domain">
+					<a class="text-cutoff" href="#{{.Domain}}" title="{{.Domain}}">{{.Domain}}</a>
+				</div>
+				<div class="public_comment">
+					<p>
+						{{.PublicComment}}
+					</p>
+				</div>
+			</div>
+			{{end}}
+		</div>
+	</section>
+</main>
+{{ template "footer.tmpl" .}}