all fields are required

app/assets/stylesheets/application.sass

@@ -18,3 +18,8 @@
 
 body
   padding-top: 20px
+  
+  #new_supporter
+    label.required
+      abbr
+        display: none

app/controllers/supporters_controller.rb

@@ -18,6 +18,6 @@ class SupportersController < ApplicationController
   private
 
   def supporter_form_params
-    params.require(:supporter).permit(:first_name, :last_name, :street, :zip, :email, :support, :age_category)
+    params.require(:supporter).permit(:first_name, :last_name, :street, :zip, :email, :support, :age_category, :city)
   end
 end

app/models/supporter.rb

@@ -11,6 +11,11 @@ class Supporter
   field :support,      type: String # Indicates the type of support
   field :age_category, type: String
 
+  validates :first_name,   presence: true
+  validates :last_name,    presence: true
+  validates :street,       presence: true
+  validates :zip,          presence: true
+  validates :city,         presence: true
   validates :email,        presence: true, uniqueness: true
   validates :support,      presence: true
   validates :age_category, presence: true