feat: advanced maintenance modes (#3977)

* feat: low maintenance mode (maintenance with admin access) (#3975)
* feat: low maintenance mode (maintenance with admin access)
* Apply fixes from StyleCI
* chore: only required when basic
* chore: more concise code
* chore(review): enum
* feat: enable through settings
* Apply fixes from StyleCI
* core: typing
* feat: safe mode (#3978)
* feat: safe mode
* feat: add extension page warning
* feat: `safe_mode_extensions`
* Apply fixes from StyleCI

framework/core/views/error/maintenance.blade.php

@@ -0,0 +1,14 @@
+@extends('flarum.forum::layouts.basic')
+
+@section('title', $translator->trans('core.views.error.maintenance_mode_title'))
+
+@section('content')
+  <p>
+    {{ $translator->trans('core.views.error.maintenance_mode_message') }}
+  </p>
+  <p>
+      <a href="{{ $url->to('forum')->route('maintenance.login') }}">
+          {{ $translator->trans('core.views.error.maintenance_mode_link') }}
+      </a>
+  </p>
+@endsection

framework/core/views/log-in.blade.php

@@ -0,0 +1,38 @@
+@extends('flarum.forum::layouts.basic')
+
+@section('title', $translator->trans('core.views.log_in.title'))
+
+@section('content')
+    @if ($errors->any())
+        <div class="errors">
+            <ul>
+                @foreach ($errors->all() as $error)
+                    <li>{{ $error }}</li>
+                @endforeach
+            </ul>
+        </div>
+    @endif
+
+    <form class="form" method="POST" action="{{ $url->to('forum')->route('login') }}">
+        <input type="hidden" name="csrfToken" value="{{ $csrfToken }}">
+
+        <p class="form-group">
+            <input type="text" class="form-control" name="identification" placeholder="{{ $translator->trans('core.views.log_in.username_or_email_placeholder') }}" aria-label="{{ $translator->trans('core.views.log_in.username_or_email_placeholder') }}">
+        </p>
+
+        <p class="form-group">
+            <input type="password" class="form-control" name="password" autocomplete="current-password" placeholder="{{ $translator->trans('core.views.log_in.password_placeholder') }}" aria-label="{{ $translator->trans('core.views.log_in.password_placeholder') }}">
+        </p>
+
+        <p class="form-group">
+            <label>
+                <input type="checkbox" name="remember" value="1" tabindex="1">
+                <span>{{ $translator->trans('core.views.log_in.remember_me_label') }}</span>
+            </label>
+        </p>
+
+        <p class="form-group">
+            <button type="submit" class="button">{{ $translator->trans('core.views.log_in.submit_button') }}</button>
+        </p>
+    </form>
+@endsection