Finish Persims consolidation

backend/web/signin.js

@@ -0,0 +1,26 @@
+document.getElementById('signin').onsubmit = async event => {
+  event.preventDefault();
+  const form = event.currentTarget;
+  const status = document.getElementById('status');
+  const action = event.submitter.value;
+  const password = document.getElementById('password');
+  const payload = {name: document.getElementById('name').value, password: password.value};
+  password.value = '';
+  for (const button of form.querySelectorAll('button')) button.disabled = true;
+  try {
+    const response = await fetch('/api/auth/' + action, {
+      method: 'POST', credentials: 'same-origin',
+      headers: {'Content-Type': 'application/json'}, body: JSON.stringify(payload)
+    });
+    payload.password = '';
+    if (!response.ok) throw new Error();
+    location.assign('/');
+  } catch {
+    payload.password = '';
+    status.textContent = 'Sign-in unavailable. Check details and retry.';
+    for (const button of form.querySelectorAll('button')) button.disabled = false;
+  }
+};
+
+fetch('/api/session', {credentials: 'same-origin', cache: 'no-store'})
+  .then(response => { if (response.ok) location.replace('/'); }).catch(() => {});