add /tu/{proposal_id} (get, post) routes

This commit ports the `/tu/?id={proposal_id}` PHP routes to
FastAPI into two individual GET and POST routes.

With this port of the single proposal view and POST logic,
several things have changed.

- The only parameter used is now `decision`, which
  must contain `Yes`, `No`, or `Abstain` as a string.
  When an invalid value is given, a BAD_REQUEST response
  is returned in plaintext: Invalid 'decision' value.
- The `doVote` parameter has been removed.
- The details section has been rearranged into a set
  of divs with specific classes that can be used for
  testing. CSS has been added to persist the layout with
  the element changes.
- Several errors that can be discovered in the POST path
  now trigger their own non-200 HTTPStatus codes.

Signed-off-by: Kevin Morris <kevr@0cost.org>

templates/partials/tu/proposal/details.html

@@ -0,0 +1,106 @@
+<h2>{% trans %}Proposal Details{% endtrans %}</h2>
+
+{% if voteinfo.is_running() %}
+    <p class="vote-running" style="font-weight: bold; color: red">
+        {% trans %}This vote is still running.{% endtrans %}
+    </p>
+{% endif %}
+
+<!-- The margin style here mimics the margin on the old <p> element. -->
+<div class="proposal details">
+    <div class="field user">
+        {{ "User" | tr }}:
+        <strong>
+            {% if voteinfo.User %}
+                <a href="{{ '/packages/?K=%s&SeB=m' | format(voteinfo.User)}}">
+                    {{ voteinfo.User }}
+                </a>
+            {% else %}
+                N/A
+            {% endif %}
+        </strong>
+    </div>
+
+    {% set submitted = voteinfo.Submitted | dt | as_timezone(timezone) %}
+    {% set end = voteinfo.End | dt | as_timezone(timezone) %}
+    <div class="field submitted">
+        {{
+            "Submitted: %s by %s" | tr
+            | format(submitted.strftime("%Y-%m-%d %H:%M"),
+                     voteinfo.Submitter.Username | e)
+        }}
+    </div>
+
+    <div class="field end">
+        {{ "End" | tr }}:
+        <strong>
+            {{ end.strftime("%Y-%m-%d %H:%M") }}
+        </strong>
+    </div>
+
+    {% if not voteinfo.is_running() %}
+        <div class="field result">
+            {{ "Result" | tr }}:
+            {% if not voteinfo.ActiveTUs %}
+                <span>{{ "unknown" | tr }}</span>
+            {% elif accepted %}
+                <span style="color: green; font-weight: bold">
+                    {{ "Accepted" | tr }}
+                </span>
+            {% else %}
+                <span style="color: red; font-weight: bold">
+                    {{ "Rejected" | tr }}
+                </span>
+            {% endif %}
+        </div>
+    {% endif %}
+</div>
+
+<div class="proposal agenda">
+    <p class="field agenda">
+        <!-- The `e` filter manually escapes content. -->
+        {{ voteinfo.Agenda | replace("\n", "<br />\n") | safe | e }}
+    </p>
+</div>
+
+<table class="vote-status">
+    <tr>
+        {% if not voteinfo.is_running() %}
+            <th>{{ "Yes" | tr }}</th>
+            <th>{{ "No" | tr }}</th>
+            <th>{{ "Abstain" | tr }}</th>
+        {% endif %}
+
+        <th>{{ "Total" | tr }}</th>
+        <th>{{ "Voted" | tr }}</th>
+        <th>{{ "Participation" | tr }}</th>
+    </tr>
+
+    <tr>
+        {% if not voteinfo.is_running() %}
+            <td>{{ voteinfo.Yes }}</td>
+            <td>{{ voteinfo.No }}</td>
+            <td>{{ voteinfo.Abstain }}</td>
+        {% endif %}
+
+        <td>{{ voteinfo.total_votes() }}</td>
+        <td>
+            {% if not has_voted %}
+                <span style="color: red; font-weight: bold">
+                    {{ "No" | tr }}
+                </span>
+            {% else %}
+                <span style="color: green; font-weight: bold">
+                    {{ "Yes" | tr }}
+                </span>
+            {% endif %}
+        </td>
+        <td>
+            {% if voteinfo.ActiveTUs %}
+                {{ (participation * 100) | number_format(2) }}%
+            {% else %}
+                {{ "unknown" | tr }}
+            {% endif %}
+        </td>
+    </tr>
+</table>

templates/partials/tu/proposal/form.html

@@ -0,0 +1,14 @@
+<form class="action-form" action="/tu/{{ proposal }}" method="POST">
+    <!-- Translate each button's text but leave the value alone. -->
+    <fieldset>
+        <button type="submit" class="button" name="decision" value="Yes">
+            {{ "Yes" | tr }}
+        </button>
+        <button type="submit" class="button" name="decision" value="No">
+            {{ "No" | tr }}
+        </button>
+        <button type="submit" class="button" name="decision" value="Abstain">
+            {{ "Abstain" | tr }}
+        </button>
+    </fieldset>
+</form>

templates/partials/tu/proposal/voters.html

@@ -0,0 +1,10 @@
+<h2>{{ "Voters" | tr }}</h2>
+<ul id="voters">
+    {% for voter in voters %}
+        <li>
+            <a href="/account/{{ voter.Username | urlencode }}">
+                {{ voter.Username | e }}
+            </a>
+        </li>
+    {% endfor %}
+</ul>

templates/tu/show.html

@@ -0,0 +1,20 @@
+{% extends "partials/layout.html" %}
+
+{% block pageContent %}
+    <div class="box">
+        {% include "partials/tu/proposal/details.html" %}
+    </div>
+
+    <div class="box">
+        {% include "partials/tu/proposal/voters.html" %}
+    </div>
+
+    <div class="box">
+        {% if error %}
+            <span class="status">{{ error | tr }}</span>
+        {% else %}
+            {% include "partials/tu/proposal/form.html" %}
+        {% endif %}
+    </div>
+
+{% endblock %}