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

app/controllers/issue/exchange_rate_provider_missings_controller.rb

@@ -0,0 +1,19 @@
+class Issue::ExchangeRateProviderMissingsController < ApplicationController
+  before_action :set_issue, only: :update
+
+  def update
+    Setting.synth_api_key = exchange_rate_params[:synth_api_key]
+    @issue.issuable.sync_later
+    redirect_back_or_to account_path(@issue.issuable)
+  end
+
+  private
+
+    def set_issue
+      @issue = Current.family.issues.find(params[:id])
+    end
+
+    def exchange_rate_params
+      params.require(:issue_exchange_rate_provider_missing).permit(:synth_api_key)
+    end
+end

app/controllers/issues_controller.rb

@@ -0,0 +1,13 @@
+class IssuesController < ApplicationController
+  before_action :set_issue, only: :show
+
+  def show
+    render template: "#{@issue.class.name.underscore.pluralize}/show", layout: "issues"
+  end
+
+  private
+
+    def set_issue
+      @issue = Current.family.issues.find(params[:id])
+    end
+end