Account Issue Model and Resolution Flow + Troubleshooting guides (#1090)

* Rough draft of issue system

* Simplify design

* Remove stale files from merge conflicts

* STI for issues

* Cleanup

* Improve Synth api key flow

* Stub api key for test

config/routes.rb

@@ -102,6 +102,12 @@ Rails.application.routes.draw do
 
   resources :institutions, except: %i[ index show ]
 
+  resources :issues, only: :show
+
+  namespace :issue do
+    resources :exchange_rate_provider_missings, only: :update
+  end
+
   # For managing self-hosted upgrades and release notifications
   resources :upgrades, only: [] do
     member do