Implement account creation; add base class FormData to validate forms

public/static/style.css

@@ -158,13 +158,27 @@ table.bordered_table th {
 
 /* --- Boxes --- */
 .filter_options,
-.edit_box,
+.form_box,
 .confirmation_box {
     border: 1px solid #999999;
     padding: 1rem;
     margin: 1rem 0;
 }
 
+/* --- Detail boxes --- */
+details {
+    margin: 1rem 0;
+}
+
+details > summary {
+    cursor: pointer;
+}
+
+details > p {
+    margin: 0.75rem 1rem;
+    font-family: monospace;
+}
+
 /* --- Detail columns --- */
 input#show_details_checkbox {
     margin-bottom: 1rem;
@@ -174,8 +188,8 @@ input#show_details_checkbox:not(:checked) ~ table .detail_column {
     display: none;
 }
 
-/* --- Edit box --- */
-.edit_box p:last-child {
+/* --- Form box --- */
+.form_box p:last-child {
     margin-bottom: 0;
 }