Basic donation records

Adds donation model/table and basic manual management in the admin
panel, as well as basic listing of users' own donations.

app/views/admin/donations/_form.html.erb

@@ -0,0 +1,53 @@
+<%= form_with(url: url, model: donation, local: true) do |form| %>
+  <% if donation.errors.any? %>
+    <div id="error_explanation">
+      <h3><%= pluralize(donation.errors.count, "error") %> prohibited this donation from being saved:</h3>
+      <ul>
+        <% donation.errors.full_messages.each do |message| %>
+          <li><%= message %></li>
+        <% end %>
+      </ul>
+    </div>
+  <% end %>
+
+  <div class="field">
+    <p>
+      <%= form.label :user_id %>
+      <%= form.collection_select :user_id, User.where(ou: "kosmos.org").order(:cn), :id, :cn %>
+    </p>
+  </div>
+
+  <div class="field">
+    <p>
+      <%= form.label :amount_sats, "Amount BTC (sats)" %>
+      <%= form.number_field :amount_sats %>
+    </p>
+  </div>
+
+  <div class="field">
+    <p>
+      <%= form.label :amount_eur, "Amount EUR (cents)" %>
+      <%= form.number_field :amount_eur %>
+    </p>
+  </div>
+
+  <div class="field">
+    <p>
+      <%= form.label :amount_usd, "Amount USD (cents)"%>
+      <%= form.number_field :amount_usd %>
+    </p>
+  </div>
+
+  <div class="field">
+    <p>
+      <%= form.label :public_name %>
+      <%= form.text_field :public_name %>
+    </p>
+  </div>
+
+  <div class="actions">
+    <p>
+      <%= form.submit %>
+    </p>
+  </div>
+<% end %>