add user signup flow

app/templates/users/sign_up.html

@@ -0,0 +1,24 @@
+{% from 'common/macros.html' import subheader %}
+{%- extends 'base.html' -%}
+{%- block title -%}sign up{%- endblock -%}
+{%- block content -%}
+{%- set welcome -%}
+Please read the rules etc. stub
+{%- endset -%}
+{{ subheader('Sign up', welcome)}}
+{%- if request.args.get('error') -%}
+<div class="infobox plank critical">
+  {{request.args.get('error')}}
+</div>
+{%- endif -%}
+<form class="plank primary-bg full-width" method="POST">
+  <label for="username">Username</label>
+  <input type="text" id="username" name="username" pattern="[a-zA-Z0-9_\-]{3,20}" title="3-20 characters. Only upper and lowercase letters, digits, hyphens, and underscores" autocomplete="username" required>
+  <label for="password">Create password</label>
+  <input type="password" id="password" name="password" pattern="(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[\W_])(?!.*\s).{10,255}" title="10+ chars with: 1 uppercase, 1 lowercase, 1 number, 1 special char, and no spaces" autocomplete="new-password" required>
+  <label for="password2">Confirm password</label>
+  <input type="password" id="password2" name="password" pattern="(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[\W_])(?!.*\s).{10,255}" title="10+ chars with: 1 uppercase, 1 lowercase, 1 number, 1 special char, and no spaces" autocomplete="new-password" required>
+  <span><input type="checkbox" name="remember" id="remember"> <label for="remember">Remember me</label></span>
+  <input type="submit" value="Sign up">
+</form>
+{%- endblock -%}