Fix add validation to webpush subscription keys (#30542)

spec/fabricators/web_push_subscription_fabricator.rb

@@ -2,6 +2,10 @@
 
 Fabricator(:web_push_subscription, from: Web::PushSubscription) do
   endpoint   Faker::Internet.url
-  key_p256dh Faker::Internet.password
-  key_auth   Faker::Internet.password
+  key_p256dh do
+    curve = OpenSSL::PKey::EC.generate('prime256v1')
+    ecdh_key = curve.public_key.to_bn.to_s(2)
+    Base64.urlsafe_encode64(ecdh_key)
+  end
+  key_auth { Base64.urlsafe_encode64(Random.new.bytes(16)) }
 end