Allow platform admins to change user auth in the UI

So we do not have to go into the db when we need to change user
auth.

We do not allow this for users who use webauthn. We do not want to
enable security downgrade for those users.

app/main/views/find_users.py

@@ -1,11 +1,11 @@
-from flask import flash, redirect, render_template, request, url_for
+from flask import abort, flash, redirect, render_template, request, url_for
 from flask_login import current_user
 from notifications_python_client.errors import HTTPError
 
 from app import user_api_client
 from app.event_handlers import create_archive_user_event
 from app.main import main
-from app.main.forms import SearchUsersByEmailForm
+from app.main.forms import AuthTypeForm, SearchUsersByEmailForm
 from app.models.user import User
 from app.utils.user import user_is_platform_admin
 
@@ -50,3 +50,23 @@ def archive_user(user_id):
     else:
         flash('There\'s no way to reverse this! Are you sure you want to archive this user?', 'delete')
         return user_information(user_id)
+
+
+@main.route("/users/<uuid:user_id>/change_auth", methods=['GET', 'POST'])
+@user_is_platform_admin
+def change_user_auth(user_id):
+    user = User.from_id(user_id)
+    if user.webauthn_auth:
+        abort(403)
+
+    form = AuthTypeForm(auth_type=user.auth_type)
+
+    if form.validate_on_submit():
+        user.update(auth_type=form.auth_type.data)
+        return redirect(url_for('.user_information', user_id=user_id))
+
+    return render_template(
+        'views/find-users/auth_type.html',
+        form=form,
+        user=user,
+    )