Display email address that invitee will be registered with.

Also add flash message for users who already have an account.

app/main/views/invites.py

@@ -33,6 +33,7 @@ def accept_invite(token):
         session['invited_user'] = invited_user.serialize()
 
         if existing_user:
+
             user_api_client.add_user_to_service(invited_user.service,
                                                 existing_user.id,
                                                 invited_user.permissions)

app/main/views/register.py

@@ -51,7 +51,7 @@ def register_from_invite():
     form.service.data = invited_user['service']
     form.email_address.data = invited_user['email_address']
 
-    return render_template('views/register-from-invite.html', form=form)
+    return render_template('views/register-from-invite.html', email_address=invited_user['email_address'], form=form)
 
 
 def _do_registration(form, service=None):

app/main/views/sign_in.py

@@ -45,6 +45,11 @@ def sign_in():
         # Vague error message for login in case of user not known, locked, inactive or password not verified
         flash('Username or password is incorrect')
 
+    invited_user = session.get('invited_user')
+    if invited_user:
+        message = 'You already have an account with GOV.UK Notify. Sign in to your account to accept this invitation.'
+        flash(message, 'default')
+
     return render_template('views/signin.html', form=form)